#include <bits/stdc++.h>
using namespace std;
int main(){
  int N;
  cin >> N;
  string S;
  cin >> S;
  string T;
  cin >> T;
  bool ok = true;
  for (int i = 0; i < N; i++){
    bool s = false, t = false;
    if (S[i] == '0' && S[N + i] == '0'){
      s = true;
    }
    if (T[i] == '0' && T[N + i] == '0'){
      t = true;
    }
    if (s ^ t){
      ok = false;
      assert(false);
      cout << -1 << endl;
      break;
    }
  }
  if (!ok){
    cout << -1 << endl;
  }
}