/** Starting in the top left corner of a 2*2 grid, there are 6 routes (without backtracking) to the bottom right corner.
How many routes are there through a 20*20 grid? */


#include "0.hpp"

#define _max 20

int main()
{
  double pro = 1.0;
  for(int i = 1; i <= _max; i++) {
    pro *= (i + (double)_max);
    pro /= i;
  }
  
  cout << (long long int)pro << endl;
  
  return 0;
}