# Create an n x n square matrix, where all the sub-matrix have the sum of opposite corner elements as even in Python 
 // C++ program for
// the above approach
#include <bits/stdc++.h>
using namespace std;


void sub_mat_even(int N)
{
  // Counter to initialize
  // the values in 2-D array
  int K = 1;
   
  // To create a 2-D array
  // from to 1 to N*2
  int A[N][N];
   
  for(int i = 0; i < N; i++)
  {
    for(int j = 0; j < N; j++)
    {
      A[i][j] = K;
      K++;
    }
  }


  // If found even we reverse
  // the alternate row elements
  // to get all diagonal elements
  // as all even or all odd
  if(N % 2 == 0)
  {
    for(int i = 0; i < N; i++)
    {
      if(i % 2 == 1)
      {
        int s = 0;
        int l = N - 1;
         
        // Reverse the row
        while(s < l)
        {
          swap(A[i][s],
               A[i][l]);
          s++;
          l--;
        }
      }
    }
  }


  // Print the formed array
  for(int i = 0; i < N; i++)
  {
    for(int j = 0; j < N; j++)
    {
      cout << A[i][j] << " ";
    }
    cout << endl;
  }
}


// Driver code
int main()
{
    int N = 4;
   
    // Function call
    sub_mat_even(N);
}


// This code is contributed by mishrapriyanshu557