#include <bits/stdc++.h>
using namespace std;
 
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
 
    int N;
    cin >> N;
    string SS, SK, SH;
    cin >> SS >> SK >> SH;
 
    int idxS = -1, idxK = -1;
 
    for (int i = 0; i < N; i++) {
        char a = SS[i], b = SK[i], c = SH[i];
        if (a != b && b != c) {
            // 셋 다 다름: 이 칸은 S-only도 되고 K-only도 됨.
            if (idxS == -1) idxS = i;
            else if (idxK == -1) idxK = i;
        } else if (b == c && a != b) {
            // K=H ≠ S => S-only 가능
            if (idxS == -1) idxS = i;
        } else if (a == c && b != a) {
            // S=H ≠ K => K-only 가능
            if (idxK == -1) idxK = i;
        }
    }
 
    if (idxS == -1 || idxK == -1) {
        cout << -1 << "\n";
        return 0;
    }
 
    string S(N, 'a');
    // 우선 아무도 점수 못 받게
    for (int i = 0; i < N; i++) {
        char a = SS[i], b = SK[i], c = SH[i];
        char pick = 'a';
        if (pick == a || pick == b || pick == c) {
            for (char ch = 'a'; ch <= 'z'; ch++) {
                if (ch != a && ch != b && ch != c) {
                    pick = ch;
                    break;
                }
            }
        }
        S[i] = pick;
    }
 
    // S-only 자리
    S[idxS] = SS[idxS];
    // K-only 자리 (S-only랑 겹치지 않음 보장됨)
    S[idxK] = SK[idxK];
 
    cout << S << "\n";
    return 0;
}

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