/* -*- coding: utf-8 -*-
 *
 * 1377.cc:  No.1377 Half xor Half - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 500;
const int MAX_N2 = MAX_N * 2;

/* typedef */

/* global variables */

char s[MAX_N2 + 4], t[MAX_N2 + 4];
int xs[MAX_N2];

/* subroutines */

/* main */

int main() {
  int n;
  scanf("%d%s%s", &n, s, t);
  int n2 = n * 2;

  int m = 0;
  for (int i = 0; i < n; i++) {
    int p0 = s[i] - '0', p1 = s[i + n] - '0';
    int q0 = t[i] - '0', q1 = t[i + n] - '0';
    if (p0 == q0 && p1 == q1) continue;

    if ((p0 + p1 == 0 && q0 + q1 != 0) ||
	(p0 + p1 != 0 && q0 + q1 == 0)) {
      puts("-1"); return 0;
    }

    if ((p0 ^ p1) == q0 && p0 == q1)
      xs[m++] = i, xs[m++] = i + 1;
    else if (p1 == q0 && (p0 ^ p1) == q1)
      xs[m++] = i + n, xs[m++] = (i + n + 1) % n2;
  }

  printf("%d\n", m);
  for (int i = 0; i < m; i++) printf("%d\n", xs[i]);
  return 0;
}