#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i = 0; i < n; i++)
#define rep2(i, x, n) for(int i = x; i <= n; i++)
#define rep3(i, x, n) for(int i = x; i >= n; i--)
#define each(e, v) for(auto &e: v)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define sz(x) (int)x.size()
using ll = long long;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
const int MOD = 1000000007;
//const int MOD = 998244353;
const int inf = (1<<30)-1;
const ll INF = (1LL<<60)-1;
template<typename T> bool chmax(T &x, const T &y) {return (x < y)? (x = y, true) : false;};
template<typename T> bool chmin(T &x, const T &y) {return (x > y)? (x = y, true) : false;};

struct io_setup{
    io_setup(){
        ios_base::sync_with_stdio(false);
        cin.tie(NULL);
        cout << fixed << setprecision(15);
    }
} io_setup;

int main(){
    int N; cin >> N;
    string S, T; cin >> S >> T;

    vector<int> ans;

    rep(i, N){
        int a = S[i]-'0', b = S[N+i]-'0', c = T[i]-'0', d = T[N+i]-'0';
        if(a == c && b == d) continue;

        if(a+b == 0 || c+d == 0) {cout << "-1\n"; return 0;}
        a ^= b, b ^= a;
        if(a == c && b == d) ans.eb(i), ans.eb(i+1);
        else ans.eb(i+1), ans.eb(i);
    }

    cout << sz(ans) << '\n';
    each(e, ans) cout << e << '\n';
}