#include <iostream>
using namespace std;
const int MAX_SIZE = 20;
int main() {
int n;
cin >> n;
char mt[MAX_SIZE][MAX_SIZE];
// Citirea matricei
for (int i = 0; i < n; ++i) {
for (int j = 0; j < n; ++j) {
cin >> mt[i][j];
}
}
// Generarea matricei modificate
for (int i = 1; i < n; ++i) {
for (int j = 0; j < n; ++j) {
mt[i][j] = mt[i - 1][j] + 1; // Incrementăm fiecare caracter cu 1
if (mt[i][j] > 'z') { // Dacă depășește 'z', revenim la 'a'
mt[i][j] = 'a';
}
}
}
// Construirea parolei finale
string password;
for (int i = 0; i < n; ++i) {
for (int j = 0; j < n; ++j) {
password += mt[i][j];
}
}
cout << password << endl;
return 0;
}
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