#include <bits/stdc++.h>
using namespace std;
int main(){
  int N;
  cin >> N;
  string S;
  cin >> S;
  string T;
  cin >> T;
  string S2;
  for (int i = 0; i < N; i++){
    if (S[i] == '0' && S[N + i] == '0'){
      S2 += '#';
    }
    if (S[i] == '0' && S[N + i] == '1'){
      S2 += 'A';
    }
    if (S[i] == '1' && S[N + i] == '0'){
      S2 += 'B';
    }
    if (S[i] == '1' && S[N + i] == '1'){
      S2 += 'C';
    }
  }
  string T2;
  for (int i = 0; i < N; i++){
    if (T[i] == '0' && T[N + i] == '0'){
      T2 += '#';
    }
    if (T[i] == '0' && T[N + i] == '1'){
      T2 += 'A';
    }
    if (T[i] == '1' && T[N + i] == '0'){
      T2 += 'B';
    }
    if (T[i] == '1' && T[N + i] == '1'){
      T2 += 'C';
    }
  }
  bool ok = true;
  vector<int> x;
  for (int i = 0; i < N; i++){
    if (S2[i] != T2[i]){
      if (S2[i] == '#' || T2[i] == '#'){
        ok = false;
      }
      if (S2[i] == 'A' && T2[i] == 'B' || S2[i] == 'B' && T2[i] == 'C' || S2[i] == 'C' && T2[i] == 'A'){
        x.push_back(i);
        x.push_back(i + 1);
      }
      if (S2[i] == 'A' && T2[i] == 'C' || S2[i] == 'C' && T2[i] == 'B' || S2[i] == 'B' && T2[i] == 'A'){
        x.push_back(i + 1);
        x.push_back(i);
      }
    }
  }
  if (!ok){
    cout << -1 << endl;
  } else {
    int M = x.size();
    cout << M << endl;
    for (int i = 0; i < M; i++){
      cout << x[i] << endl;
    }
  }
}