#include <iostream>
#include <fstream>
using namespace std;

int main()
{
  cout << "Enter a number: ";
  int n;
  cin >> n;


  for( int i=0; i<n; i++ )
  {
    for(int j=0; j<n; j++ )
    {
      if ( j == i || j == n-i-1 )
        cout << "@";
      else
        cout << ".";
    }

    cout << endl;
  }

  return 0;
}