#include <iostream>
#include <string>
using namespace std;
int main()
{
char A[10][10], cuvant[10];
int N, i, j;
cout<<"N="; cin>>N;
for(i=0;i<N;i++)
for(j=0;j<N;j++){
cout<<"A["<<i<<"]["<<j<<"]="; cin>>A[i][j];
}
for(i=0;i<N;i++)
cuvant[i]=A[i][i];
cuvant[i]='\0';
cout<<cuvant;
return 0;
}