#include <stdio.h>

// Starting in the top left corner of a 22 grid, there are 6 routes (without backtracking) to the bottom right corner.


// How many routes are there through a 2020 grid?
#define GRID_SIZE 20

int traverse(int x, int y);

int main() {
    printf("%d", traverse(0, 0));

    return 1;
}

int traverse(int x, int y) {
    int i = 0;

    if(x < GRID_SIZE) {
        i += traverse(x + 1, y);
    }
    if(y < GRID_SIZE) {
        i += traverse(x, y + 1);
    }

    if(x == GRID_SIZE && y == GRID_SIZE) {
        return 1;
    }

    return i;
}