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;
template <typename A, typename B, typename C>
struct triple {
  A X;
  B Y;
  C Z;
  triple(A a = 0, B b = 0, C c = 0) : X(a), Y(b), Z(c) {}
};
template <typename A, typename B, typename C>
triple<A, B, C> make_triple(A a = 0, B b = 0, C c = 0) {
  return triple<A, B, C>(a, b, c);
}
template <typename A, typename B, typename C>
bool operator<(const triple<A, B, C>& a, const triple<A, B, C>& b) {
  if (a.X != b.X) return a.X < b.X;
  if (a.Y != b.Y) return a.Y < b.Y;
  return a.Z < b.Z;
}
template <typename T, typename SS>
ostream& operator<<(ostream& ofs, const pair<T, SS>& p) {
  ofs << "( " << p.first << " , " << p.second << " )";
  return ofs;
}
template <typename T>
void print(T a) {
  for (auto i : a) cout << i << ' ';
  cout << '\n';
}
template <typename T>
T max(T a, T b, T c) {
  return max(a, max(b, c));
}
template <typename T>
T min(T a, T b, T c) {
  return min(a, min(b, c));
}
struct custom_hash {
  static uint64_t splitmix64(uint64_t x) {
    x += 0x9e3779b97f4a7c15;
    x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
    x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
    return x ^ (x >> 31);
  }
  size_t operator()(uint64_t x) const {
    static const uint64_t FIXED_RANDOM =
        chrono::steady_clock::now().time_since_epoch().count();
    return splitmix64(x + FIXED_RANDOM);
  }
};
signed main() {
  srand(time(NULL));
  cin.tie(0);
  cout.tie(0);
  ios_base::sync_with_stdio(false);
  long long n;
  cin >> n;
  string s, t;
  cin >> s >> t;
  vector<long long> a(n);
  for (long long i = 0; i < (n); i++)
    if (s[i] != t[i]) a[i] = (s[i] == '1' ? 1 : -1);
  long long z = 0;
  long long ans = 0, now = 0;
  for (long long i = 0; i < (n); i++) {
    now += a[i];
    ans = max(ans, now);
    now = max(now, 0LL);
  }
  z = max(z, ans);
  for (long long i = 0; i < (n); i++) a[i] = -a[i];
  now = ans = 0;
  for (long long i = 0; i < (n); i++) {
    now += a[i];
    ans = max(ans, now);
    now = max(now, 0LL);
  }
  z = max(z, ans);
  sort(s.begin(), s.end());
  sort(t.begin(), t.end());
  if (s != t)
    cout << "-1\n";
  else
    cout << z << '\n';
}
