// Example program
#include <iostream>
#include <string>

using namespace std;

int main()
{
  int matrix[4][4] = {
   {1, 2, 3, 4},
   {5, 6, 7, 8},
   {9, 10, 11, 12},
   {13, 14, 15, 16}
  };
  int diagonal[4] = {};
  
  for (int i = 0; i < 4; i++) {
       diagonal[i] = matrix[i][i];
       cout<<diagonal[i]<<", ";
    }
}