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.IOException;
  import java.io.InputStream;
  import java.math.BigInteger;
  import java.util.*;
  
  public class Main {
  
      public static void main(String[] args) {
          // write your code here
          boolean readFromLocal = true;
          //readFromLocal = false;
          String filepath = "src/input.txt";
          //FileInputStream fileInputStream = new FileInputStream(filepath);
          InputReader inputReader = new InputReader(System.in);
          Solve s = new Solve();
          s.solve(inputReader);
      }
  }
  
  class Solve {
  
      public void solve(InputReader inputReader) {
          int t = inputReader.nextInt();
          long mod = 1000_000_000 + 9;
  
          while (t > 0) {
              t--;
              int n = inputReader.nextInt();
              char[] a = inputReader.nextString().toCharArray();
              char[] b = inputReader.nextString().toCharArray();
              int aLit = countLit(a);
              int bLit = countLit(b);
              int res = Integer.MAX_VALUE;
              if (aLit==bLit) {
                  res = Math.min(res,findDiff(a,b));
              }
              if(n-aLit+1 == bLit) {
                  applyOperation(a,b);
                  res = Math.min(res,1+findDiff(a,b));
              }
              System.out.println((res==Integer.MAX_VALUE?-1:res));
          }
      }
  
      private int findDiff(char[] a, char[] b) {
          int diff = 0;
          for (int i = 0; i < a.length; i++) {
              if(a[i]!=b[i]){
                  diff++;
              }
          }
          return diff;
      }
  
      private void applyOperation(char[] a, char[] b) {
          for (int i = 0; i < a.length; i++) {
              if (a[i]=='1' && b[i]=='1'){
                  a[i] = '0';
                  break;
              }
          }
          for (int i = 0; i < a.length; i++) {
              a[i] = a[i]=='1'?'0':'1';
          }
      }
  
      private int countLit(char[] s) {
          int lit = 0;
          for (int i = 0; i < s.length; i++) {
              if (s[i]=='1') lit++;
          }
          return lit;
  
      }
  }
  
  class Pair implements Comparable<Pair> {
      int first,second;
  
      public Pair(int first, int second) {
          this.first = first;
          this.second = second;
      }
  
      @Override
      public int compareTo(Pair o) {
          return this.second - o.second;
      }
  }
  class Utils {
      static void swap(int[] res, int i, int j) {
          int temp = res[i];
          res[i] = res[j];
          res[j] = temp;
      }
  
      static long pow(long num, int n, long mod) {
          long res = num%mod;
          while (n > 0) {
              if ((n & 1) != 0) {
                  res = (res * num) % mod;
              }
              num = (num * num) % mod;
              n >>= 1;
          }
          return res;
      }
  
  }
  
  class InputReader {
      private boolean finished = false;
  
      private InputStream stream;
      private byte[] buf = new byte[1024];
      private int curChar;
      private int numChars;
      private SpaceCharFilter filter;
  
      public InputReader(InputStream stream) {
          this.stream = stream;
      }
  
      public int read() {
          if (numChars == -1) {
              throw new InputMismatchException();
          }
          if (curChar >= numChars) {
              curChar = 0;
              try {
                  numChars = stream.read(buf);
              } catch (IOException e) {
                  throw new InputMismatchException();
              }
              if (numChars <= 0) {
                  return -1;
              }
          }
          return buf[curChar++];
      }
  
      public int peek() {
          if (numChars == -1) {
              return -1;
          }
          if (curChar >= numChars) {
              curChar = 0;
              try {
                  numChars = stream.read(buf);
              } catch (IOException e) {
                  return -1;
              }
              if (numChars <= 0) {
                  return -1;
              }
          }
          return buf[curChar];
      }
  
      public int nextInt() {
          int c = read();
          while (isSpaceChar(c)) {
              c = read();
          }
          int sgn = 1;
          if (c == '-') {
              sgn = -1;
              c = read();
          }
          int res = 0;
          do {
              if (c < '0' || c > '9') {
                  throw new InputMismatchException();
              }
              res *= 10;
              res += c - '0';
              c = read();
          } while (!isSpaceChar(c));
          return res * sgn;
      }
  
      public long nextLong() {
          int c = read();
          while (isSpaceChar(c)) {
              c = read();
          }
          int sgn = 1;
          if (c == '-') {
              sgn = -1;
              c = read();
          }
          long res = 0;
          do {
              if (c < '0' || c > '9') {
                  throw new InputMismatchException();
              }
              res *= 10;
              res += c - '0';
              c = read();
          } while (!isSpaceChar(c));
          return res * sgn;
      }
  
      public String nextString() {
          int c = read();
          while (isSpaceChar(c)) {
              c = read();
          }
          StringBuilder res = new StringBuilder();
          do {
              if (Character.isValidCodePoint(c)) {
                  res.appendCodePoint(c);
              }
              c = read();
          } while (!isSpaceChar(c));
          return res.toString();
      }
  
      public boolean isSpaceChar(int c) {
          if (filter != null) {
              return filter.isSpaceChar(c);
          }
          return isWhitespace(c);
      }
  
      public static boolean isWhitespace(int c) {
          return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
      }
  
      private String readLine0() {
          StringBuilder buf = new StringBuilder();
          int c = read();
          while (c != '\n' && c != -1) {
              if (c != '\r') {
                  buf.appendCodePoint(c);
              }
              c = read();
          }
          return buf.toString();
      }
  
      public String readLine() {
          String s = readLine0();
          while (s.trim().length() == 0) {
              s = readLine0();
          }
          return s;
      }
  
      public String readLine(boolean ignoreEmptyLines) {
          if (ignoreEmptyLines) {
              return readLine();
          } else {
              return readLine0();
          }
      }
  
      public BigInteger readBigInteger() {
          try {
              return new BigInteger(nextString());
          } catch (NumberFormatException e) {
              throw new InputMismatchException();
          }
      }
  
      public char nextCharacter() {
          int c = read();
          while (isSpaceChar(c)) {
              c = read();
          }
          return (char) c;
      }
  
      public double nextDouble() {
          int c = read();
          while (isSpaceChar(c)) {
              c = read();
          }
          int sgn = 1;
          if (c == '-') {
              sgn = -1;
              c = read();
          }
          double res = 0;
          while (!isSpaceChar(c) && c != '.') {
              if (c == 'e' || c == 'E') {
                  return res * Math.pow(10, nextInt());
              }
              if (c < '0' || c > '9') {
                  throw new InputMismatchException();
              }
              res *= 10;
              res += c - '0';
              c = read();
          }
          if (c == '.') {
              c = read();
              double m = 1;
              while (!isSpaceChar(c)) {
                  if (c == 'e' || c == 'E') {
                      return res * Math.pow(10, nextInt());
                  }
                  if (c < '0' || c > '9') {
                      throw new InputMismatchException();
                  }
                  m /= 10;
                  res += (c - '0') * m;
                  c = read();
              }
          }
          return res * sgn;
      }
  
      public boolean isExhausted() {
          int value;
          while (isSpaceChar(value = peek()) && value != -1) {
              read();
          }
          return value == -1;
      }
  
      public String next() {
          return nextString();
      }
  
      public SpaceCharFilter getFilter() {
          return filter;
      }
  
      public void setFilter(SpaceCharFilter filter) {
          this.filter = filter;
      }
  
      public interface SpaceCharFilter {
          boolean isSpaceChar(int ch);
      }
  
      public int[] nextIntArray(int n) {
          int[] array = new int[n];
          for (int i = 0; i < n; ++i) array[i] = nextInt();
          return array;
      }
  
      public int[] nextSortedIntArray(int n) {
          int[] array = nextIntArray(n);
          Arrays.sort(array);
          return array;
      }
  
      public int[] nextSumIntArray(int n) {
          int[] array = new int[n];
          array[0] = nextInt();
          for (int i = 1; i < n; ++i) array[i] = array[i - 1] + nextInt();
          return array;
      }
  
      public long[] nextLongArray(int n) {
          long[] array = new long[n];
          for (int i = 0; i < n; ++i) array[i] = nextLong();
          return array;
      }
  
      public long[] nextSumLongArray(int n) {
          long[] array = new long[n];
          array[0] = nextInt();
          for (int i = 1; i < n; ++i) array[i] = array[i - 1] + nextInt();
          return array;
      }
  
      public long[] nextSortedLongArray(int n) {
          long[] array = nextLongArray(n);
          Arrays.sort(array);
          return array;
      }
  }