description: There are n candles on a Hanukkah menorah, and some of its candles are initially lit. We can describe which candles are lit with a binary string s, where the i-th candle is lit if and only if s_i=1.
  
  <image>
  
  Initially, the candle lights are described by a string a. In an operation, you select a candle that is currently lit. By doing so, the candle you selected will remain lit, and every other candle will change (if it was lit, it will become unlit and if it was unlit, it will become lit).
  
  You would like to make the candles look the same as string b. Your task is to determine if it is possible, and if it is, find the minimum number of operations required.
  
  Input
  
  The first line contains an integer t (1≤ t≤ 10^4) — the number of test cases. Then t cases follow.
  
  The first line of each test case contains a single integer n (1≤ n≤ 10^5) — the number of candles.
  
  The second line contains a string a of length n consisting of symbols 0 and 1 — the initial pattern of lights.
  
  The third line contains a string b of length n consisting of symbols 0 and 1 — the desired pattern of lights.
  
  It is guaranteed that the sum of n does not exceed 10^5.
  
  Output
  
  For each test case, output the minimum number of operations required to transform a to b, or -1 if it's impossible.
  
  Example
  
  Input
  
  
  5
  5
  11010
  11010
  2
  01
  11
  3
  000
  101
  9
  100010111
  101101100
  9
  001011011
  011010101
  
  
  Output
  
  
  0
  1
  -1
  3
  4
  
  Note
  
  In the first test case, the two strings are already equal, so we don't have to perform any operations.
  
  In the second test case, we can perform a single operation selecting the second candle to transform 01 into 11.
  
  In the third test case, it's impossible to perform any operations because there are no lit candles to select.
  
  In the fourth test case, we can perform the following operations to transform a into b: 
  
    1. Select the 7-th candle: 100010{\color{red}1}11→ 011101{\color{red} 1}00. 
    2. Select the 2-nd candle: 0{\color{red} 1}1101100→ 1{\color{red} 1}0010011. 
    3. Select the 1-st candle: {\color{red}1}10010011→ {\color{red}1}01101100. 
  
  
  
  In the fifth test case, we can perform the following operations to transform a into b: 
  
    1. Select the 6-th candle: 00101{\color{red}1}011→ 11010{\color{red}1}100 
    2. Select the 2-nd candle: 1{\color{red}1}0101100→ 0{\color{red}1}1010011 
    3. Select the 8-th candle: 0110100{\color{red}1}1→ 1001011{\color{red}1}0 
    4. Select the 7-th candle: 100101{\color{red}1}10→ 011010{\color{red}1}01 
solution: import java.io.OutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.PrintWriter;
  import java.lang.reflect.Array;
  import java.io.BufferedReader;
  import java.io.InputStreamReader;
  import java.util.*;
  
  public class Main {
      public static void main(String[] args){
          InputStream inputStream = System.in;
          OutputStream outputStream = System.out;
          InputReader in = new InputReader(inputStream);
          PrintWriter out = new PrintWriter(outputStream);
          solve(in, out);
          out.close();
      }
  
      static String reverse(String s) {
          return (new StringBuilder(s)).reverse().toString();
      }
  
      static void sieveOfEratosthenes(int n, int factors[], ArrayList<Integer> ar) 
      { 
          factors[1]=1;
          int p;
          for(p = 2; p*p <=n; p++) 
          { 
              if(factors[p] == 0) 
              { 
                  ar.add(p);
                  factors[p]=p;
                  for(int i = p*p; i <= n; i += p) 
                      if(factors[i]==0)
                          factors[i] = p; 
              } 
          } 
          for(;p<=n;p++){
              if(factors[p] == 0) 
              { 
                  factors[p] = p;
                  ar.add(p);
              } 
          }
      }
  
      static void sort(int ar[]) {
          int n = ar.length;
          ArrayList<Integer> a = new ArrayList<>();
          for (int i = 0; i < n; i++)
              a.add(ar[i]);
          Collections.sort(a);
          for (int i = 0; i < n; i++)
              ar[i] = a.get(i);
      }
  
      static void sort1(long ar[]) {
          int n = ar.length;
          ArrayList<Long> a = new ArrayList<>();
          for (int i = 0; i < n; i++)
              a.add(ar[i]);
          Collections.sort(a);
          for (int i = 0; i < n; i++)
              ar[i] = a.get(i);
      }
  
      static void sort2(char ar[]) {
          int n = ar.length;
          ArrayList<Character> a = new ArrayList<>();
          for (int i = 0; i < n; i++)
              a.add(ar[i]);
          Collections.sort(a);
          for (int i = 0; i < n; i++)
              ar[i] = a.get(i);
      }
  
      static long ncr(long n, long r, long mod) {
          if (r == 0)
              return 1;
          long val = ncr(n - 1, r - 1, mod);
          val = (n * val) % mod;
          val = (val * modInverse(r, mod)) % mod;
          return val;
      }
  
      static long max[];
      static long lz[];
      
      // static void build(long a[], int v, int tl, int tr) {
      //     if (tl == tr) {
      //         max[v] = a[tl];
              
      //     } else {
      //         int tm = (tl + tr) / 2;
      //         build(a, v*2, tl, tm);
      //         build(a, v*2+1, tm+1, tr);
      //         max[v] = max[v*2] + max[v*2+1];
      //     }
      // }
  
      // static void push(int v, int tl, int tr){
      //     if(tl==tr){
      //         lz[v] = 0;
      //         return;
      //     }
      //     max[2*v] += lz[v];
      //     // max[2*v] %= m;
      //     max[2*v+1] += lz[v];
      //     // max[2*v+1] %= m;
      //     lz[2*v] += lz[v];
      //     lz[2*v] %= m;
      //     lz[2*v+1] += lz[v];
      //     lz[2*v+1] %= m;
      //     lz[v] = 0;
      // }
  
      static void update(int v, int tl, int tr, int l, int r, long val) {
          if(tl>r||tr<l)
              return;
          if(tl>=l&&tr<=r){
              max[v] = Math.max(val, max[v]);
              return;
          }
          int tm = ((tl + tr) >> 1);
          update(v*2, tl, tm, l, r, val);
          update(v*2+1, tm+1, tr, l, r, val);
          max[v] = Math.max(max[2*v],max[2*v+1]);
      }
  
      static long get(int v, int tl, int tr, int l, int r) {
          if(l>tr||r<tl)
              return 0;
          if (tl >= l && tr <= r) {
              return max[v];
          }
          int tm = ((tl + tr) >> 1);
          return Math.max(get(2*v, tl, tm, l, r), get(2*v+1, tm+1, tr, l, r));
      }
  
      // static int y = 0;
  
      static int parent[];
      static int rank[];
  
      static long m = 0;
  
      static int find_set(int v) {
          if (v == parent[v])
              return v;
          return find_set(parent[v]);
      }
      
      static void make_set(int v) {
          parent[v] = v;
          rank[v] = 1;
      }
      
      static void union_sets(int a, int b) {
          a = find_set(a);
          b = find_set(b);
          if (a != b) {
              if (rank[a] < rank[b]){
                  int tmp = a;
                  a = b;
                  b = tmp;
              }
              parent[b] = a;
              // if (rank[a] == rank[b])
              //     rank[a]++;
              rank[a] += rank[b];
              max1 = Math.max(max1,rank[a]);
              // System.out.println(a+" "+b+" "+rank[a]+" "+rank[b]);
          }
      }
  
      static int parent1[];
      static int rank1[];
  
      static int find_set1(int v) {
          if (v == parent1[v])
              return v;
          return find_set1(parent1[v]);
      }
      
      static void make_set1(int v) {
          parent1[v] = v;
          rank1[v] = 1;
      }
      
      static void union_sets1(int a, int b) {
          a = find_set1(a);
          b = find_set1(b);
          if (a != b) {
              if (rank1[a] < rank1[b]){
                  int tmp = a;
                  a = b;
                  b = tmp;
              }
              parent1[b] = a;
              // if (rank1[a] == rank1[b])
              //     rank1[a]++;
              rank1[a] += rank1[b];
          }
      }
  
      static long max1 = 0;
  
      static int count = 0;
      static int count1 = 0;
  
      public static void solve(InputReader sc, PrintWriter pw){
          int i, j = 0;
          // int t = 1; 
          long mod = 998244353;
          // int factors[] = new int[1000001];
          // ArrayList<Integer> ar = new ArrayList<>();
          // sieveOfEratosthenes(1000000, factors, ar);
          // HashSet<Integer> set = new HashSet<>();
          // for(int x:ar){
          //     set.add(x);
          // }
          int t = sc.nextInt();
          u: while (t-- > 0) {
              int n = sc.nextInt();
              char a[] = sc.next().toCharArray();
              char b[] = sc.next().toCharArray();
              int c1 = 0, c2 = 0, c = -1;
              for(i=0;i<n;i++){
                  if(a[i]=='1')
                      c1++;
                  if(b[i]=='1')
                      c2++;
                  if(a[i]=='1'&&b[i]=='1')
                      c = i;
              }
              if(c1!=c2&&c1+c2!=n+1){
                  pw.println(-1);
                  continue u;
              }
              int min = Integer.MAX_VALUE;
              if(c1==c2){
                  int d = 0;
                  for(i=0;i<n;i++){
                      if(a[i]!=b[i])
                          d++;
                  }
                  min = d;
              }
              if(c1+c2==n+1){
                  int d = 0;
                  for(i=0;i<n;i++){
                      if(a[i]=='1'&&b[i]=='1')
                          d++;
                  }
                  d--;
                  min = Math.min(min,1+2*d);
              }
              pw.println(min);
          }
      }
  
      static void KMPSearch(char pat[], char txt[], int pres[]){
          int M = pat.length;
          int N = txt.length;
          int lps[] = new int[M];
          int j = 0; 
          computeLPSArray(pat, M, lps);
          int i = 0;
          while (i < N) {
              if (pat[j] == txt[i]) {
                  j++;
                  i++;
              }
              if (j == M) {
                  pres[i-1] = 1;
                  j = lps[j - 1];
              }
              else if (i < N && pat[j] != txt[i]) {
                  if (j != 0)
                      j = lps[j - 1];
                  else
                      i = i + 1;
              }
          }
      }
    
      static void computeLPSArray(char pat[], int M, int lps[])
      {
          int len = 0;
          int i = 1;
          lps[0] = 0; 
          while (i < M) {
              if (pat[i] == pat[len]) {
                  len++;
                  lps[i] = len;
                  i++;
              }
              else 
              {
                  if (len != 0) {
                      len = lps[len - 1];
                  }
                  else
                  {
                      lps[i] = len;
                      i++;
                  }
              }
          }
      }
  
      static long[][] matrixMult(long a[][], long b[][], long mod){
          int n = a.length;
          int m = a[0].length;
          int p = b[0].length;
          long c[][] = new long[n][p];
          for(int i=0;i<n;i++){
              for(int j=0;j<m;j++){
                  for(int k=0;k<p;k++){
                      c[i][k] += a[i][j]*b[j][k];
                      c[i][k] %= mod;
                  }
              }
          }
          return c;
      }
  
      static long[][] exp(long mat[][], long b, long mod){
          if(b==0){
              int n = mat.length;
              long res[][] = new long[n][n];
              for(int i=0;i<n;i++){
                  res[i][i] = 1;
              }
              return res;
          }
          long half[][] = exp(mat, b/2, mod);
          long res[][] = matrixMult(half, half, mod);
          if(b%2==1){
              res = matrixMult(res, mat, mod);
          }
          return res;
      }
  
      static void countPrimeFactors(int num, int a[], HashMap<Integer,Integer> pos){
          for(int i=2;i*i<num;i++){
              if(num%i==0){
                  int y = pos.get(i);
                  while(num%i==0){
                      a[y]++;
                      num/=i;
                  }
              }
          }
          if(num>1){
              int y = pos.get(num);
              a[y]++;
          }
      }
  
      static void assignAnc(ArrayList<Integer> ar[], int depth[], int sz[], int par[][] ,int curr, int parent, int d){
          depth[curr] = d;
          sz[curr] = 1;
          par[curr][0] = parent;
          for(int v:ar[curr]){
              if(parent==v)
                  continue;
              assignAnc(ar, depth, sz, par, v, curr, d+1);
              sz[curr] += sz[v];
          }
      }
  
      static int findLCA(int a, int b, int par[][], int depth[]){
          if(depth[a]>depth[b]){
              a = a^b;
              b = a^b;
              a = a^b;
          }
          int diff = depth[b] - depth[a];
          for(int i=19;i>=0;i--){
              if((diff&(1<<i))>0){
                  b = par[b][i];
              }
          }
          if(a==b)
              return a;
          for(int i=19;i>=0;i--){
              if(par[b][i]!=par[a][i]){
                  b = par[b][i];
                  a = par[a][i];
              }
          }
          return par[a][0];
      }
  
      static void formArrayForBinaryLifting(int n, int par[][]){
          for(int j=1;j<20;j++){
              for(int i=0;i<n;i++){
                  if(par[i][j-1]==-1)
                      continue;
                  par[i][j] = par[par[i][j-1]][j-1];
              }
          }
      }
  
      static long lcm(int a, int b){
          return a*b/gcd(a,b);
      }
  
      static class Pair1 {
          long a;
          long b;
          
          Pair1(long a, long b) {
              this.a = a;
              this.b = b;
          }
      }
  
      static class Pair implements Comparable<Pair> {
          int a;
          int b;
          // int c;
          
          Pair(int a, int b) {
              this.a = a;
              this.b = b;
              // this.c = c;
          }
   
          public int compareTo(Pair p) {
              if(a!=p.a)
                  return p.a-a;
              return b-p.b;
          }
      }
  
      static class Pair2 implements Comparable<Pair2> {
          int a;
          int b;
          int c;
          
          Pair2(int a, int b, int c) {
              this.a = a;
              this.b = b;
              this.c = c;
          }
   
          public int compareTo(Pair2 p) {
              return a-p.a;
          }
      }
  
      static boolean isPrime(int n) { 
          if (n <= 1) 
              return false; 
          if (n <= 3) 
              return true; 
          if (n % 2 == 0 ||  n % 3 == 0) 
              return false; 
          for (int i = 5; i * i <= n; i = i + 6) 
              if (n % i == 0 || n % (i + 2) == 0) 
                  return false; 
          return true; 
      } 
  
      static long gcd(long a, long b) {
          if (b == 0)
              return a;
          return gcd(b, a % b);
      }
  
      static long fast_pow(long base, long n, long M) {
          if (n == 0)
              return 1;
          if (n == 1)
              return base % M;
          long halfn = fast_pow(base, n / 2, M);
          if (n % 2 == 0)
              return (halfn * halfn) % M;
          else
              return (((halfn * halfn) % M) * base) % M;
      }
  
      static long modInverse(long n, long M) {
          return fast_pow(n, M - 2, M);
      }
  
      static class InputReader {
          public BufferedReader reader;
          public StringTokenizer tokenizer;
  
          public InputReader(InputStream stream) {
              reader = new BufferedReader(new InputStreamReader(stream), 9992768);
              tokenizer = null;
          }
  
          public String next() {
              while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                  try {
                      tokenizer = new StringTokenizer(reader.readLine());
                  } catch (IOException e) {
                      throw new RuntimeException(e);
                  }
              }
              return tokenizer.nextToken();
          }
  
          public int nextInt() {
              return Integer.parseInt(next());
          }
  
          public long nextLong() {
              return Long.parseLong(next());
          }
      }
  }