Naman has two binary strings s and t of length n (a binary string is a string which only consists of the characters "0" and "1"). He wants to convert s into t using the following operation as few times as possible.

In one operation, he can choose any subsequence of s and rotate it clockwise once.

For example, if s = 1110100, he can choose a subsequence corresponding to indices (1-based) \{2, 6, 7 \} and rotate them clockwise. The resulting string would then be s = 1010110.

A string a is said to be a subsequence of string b if a can be obtained from b by deleting some characters without changing the ordering of the remaining characters.

To perform a clockwise rotation on a sequence c of size k is to perform an operation which sets c_1:=c_k, c_2:=c_1, c_3:=c_2, …, c_k:=c_{k-1} simultaneously.

Determine the minimum number of operations Naman has to perform to convert s into t or say that it is impossible. 

Input

The first line contains a single integer n (1 ≤ n ≤ 10^6) — the length of the strings.

The second line contains the binary string s of length n.

The third line contains the binary string t of length n.

Output

If it is impossible to convert s to t after any number of operations, print -1.

Otherwise, print the minimum number of operations required.

Examples

Input


6
010000
000001


Output


1

Input


10
1111100000
0000011111


Output


5

Input


8
10101010
01010101


Output


1

Input


10
1111100000
1111100001


Output


-1

Note

In the first test, Naman can choose the subsequence corresponding to indices \{2, 6\} and rotate it once to convert s into t.

In the second test, he can rotate the subsequence corresponding to all indices 5 times. It can be proved, that it is the minimum required number of operations.

In the last test, it is impossible to convert s into t.
#include <bits/stdc++.h>
using namespace std;
long long gcd(long long a, long long b) {
  if (b > a) {
    return gcd(b, a);
  }
  if (b == 0) {
    return a;
  }
  return gcd(b, a % b);
}
long long expo(long long a, long long b, long long mod) {
  long long res = 1;
  while (b > 0) {
    if (b & 1) res = (res * a) % mod;
    a = (a * a) % mod;
    b = b >> 1;
  }
  return res;
}
vector<int> sieve(int n) {
  int *arr = new int[n + 1]();
  vector<int> vect;
  for (int i = 2; i <= n; i++)
    if (arr[i] == 0) {
      vect.push_back(i);
      for (int j = 2 * i; j <= n; j += i) arr[j] = 1;
    }
  return vect;
}
void extendgcd(long long a, long long b, long long *v) {
  if (b == 0) {
    v[0] = 1;
    v[1] = 0;
    v[2] = a;
    return;
  }
  extendgcd(b, a % b, v);
  long long x = v[1];
  v[1] = v[0] - v[1] * (a / b);
  v[0] = x;
  return;
}
long long mminv(long long a, long long b) {
  long long arr[3];
  extendgcd(a, b, arr);
  return arr[0];
}
long long mminvprime(long long a, long long b) { return expo(a, b - 2, b); }
bool revsort(long long a, long long b) { return a > b; }
void swap(int &x, int &y) {
  int temp = x;
  x = y;
  y = temp;
}
long long combination(long long n, long long r, long long m, long long *fact) {
  long long val1 = fact[n];
  long long val2 = mminvprime(fact[r], m);
  long long val3 = mminvprime(fact[n - r], m);
  return ((val1 * val2) % m * val3) % m;
}
bool comp;
bool helper(long long value, long long *arr, long long k, int start, int end) {
  long long count = 0;
  int i = start;
  while (i <= end) {
    if (arr[i] <= value) {
      count++;
      i += 2;
    } else
      i++;
  }
  if (count >= k)
    return true;
  else
    return false;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int n;
  cin >> n;
  string a, b;
  cin >> a >> b;
  int count1 = 0;
  int count2 = 0;
  int count3 = 0;
  int count4 = 0;
  for (int i = 0; i < n; i++) {
    if (a[i] == '0')
      count1++;
    else
      count2++;
    if (b[i] == '0')
      count3++;
    else
      count4++;
  }
  if (count1 != count3 || count2 != count4)
    cout << -1 << endl;
  else {
    int ans2 = 0;
    int ans1 = 0;
    int ans = 0;
    for (int i = 0; i < n; i++) {
      if (a[i] == '0' && b[i] == '1') {
        ans2++;
        ans1--;
      }
      if (a[i] == '1' && b[i] == '0') {
        ans2--;
        ans1++;
      }
      if (ans1 <= 0) ans1 = 0;
      if (ans2 <= 0) ans2 = 0;
      ans = max(ans, max(ans1, ans2));
    }
    cout << ans << endl;
  }
  return 0;
}
