#include <bits/stdc++.h>
using namespace std;
 
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
 
    int N;
    cin >> N;
    string S_S, S_K, S_H;
    cin >> S_S >> S_K >> S_H;
 
    string S = S_S; // 처음엔 숭돌이 답안으로 맞춰둠
    int idx = -1;
 
    for (int i = 0; i < N; i++) {
        // 조건: 숭돌이와 고돌이 다름 + 고돌이와 한돌이 다름
        if (S_S[i] != S_K[i] && S_K[i] != S_H[i]) {
            idx = i;
            break;
        }
    }
 
    if (idx == -1) {
        cout << -1 << "\n";
        return 0;
    }
 
    // 해당 위치를 고돌이 답으로 바꿔준다
    S[idx] = S_K[idx];
    cout << S << "\n";
    return 0;
}

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