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;
const int N = 1e6 + 10;
const int inf = 1e9;
const int mo = 998244353;
int main() {
  int n, c1 = 0, c2 = 0;
  string s1, s2;
  cin >> n >> s1 >> s2;
  vector<int> vec;
  for (auto i = (1); i <= (n); ++i) {
    if (s1[i - 1] != s2[i - 1]) vec.push_back(s1[i - 1]);
    if (s1[i - 1] == '1') c1++;
    if (s2[i - 1] == '1') c2++;
  }
  if (c1 != c2) {
    cout << "-1";
    return 0;
  }
  int cnt0 = 0, cnt1 = 0, ans = 0;
  for (auto i = (1); i <= (vec.size()); ++i) {
    int cur = vec[i - 1] - '0';
    if (cur) {
      if (cnt0) {
        cnt0--;
        cnt1++;
      } else {
        cnt1++;
        ans++;
      }
    } else {
      if (cnt1) {
        cnt1--;
        cnt0++;
      } else {
        cnt0++;
        ans++;
      }
    }
  }
  cout << ans;
  return 0;
}
