下面程序的输出为（     ）。

#include <iostream>

using namespace std;

int a[10][10];

int main() {

int m = 5, n = 4;

for (int x = 0; x <= m; x++)

a[x][0] = 1;

for (int y = 1; y <= n; y++)

a[0][y] = 1;

for (int x = 1; x <= m; x++)

for (int y = 1; y <= n; y++)

a[x][y] = a[x - 1][y] + a[x][y - 1];

cout << a[m][n] << endl;

return 0;

}