#include <bits/stdc++.h>
using namespace std;

#ifdef _RUTHEN
#include <debug.hpp>
#else
#define show(...) true
#endif

#define REP(i, n) for (int i = 0; i < (n); i++)
template <class T> using V = vector<T>;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int N;
    cin >> N;
    V<string> S(N);
    REP(i, N) cin >> S[i];
    REP(i, N) {
        char c = 1 - (S[i][i] - 'a') + 'a';
        cout << c;
    }
    cout << '\n';
    return 0;
}