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;}