Wannafly挑战赛16 A 取石子

#include<stdio.h>
#define N_max 2005
int n;
typedef long long ll;
#define mod 1000000007

ll C[N_max][N_max] = { 0 };
#define min(a,b) ((a)<(b)?(a):(b))

int main() {

int a[4];
	ll res = 1;
	for (int t = 0; t < N_max; ++t)C[t][0]=1;

	for (int i = 1; i <N_max; ++i)
		for (int j = 1; j <=i; ++j) {
			C[i][j] = (C[i - 1][j - 1] + C[i - 1][j])%mod;
		}
	for (int i = 0; i < 4; ++i)
	{
		scanf("%d", a + i);
	}
	res = C[a[0]][a[0]];
	res = res*C[a[0] + a[1]][a[1]]%mod;
	res = res*C[a[0] + a[1]+a[2]][a[2]]%mod;
	res = res*C[a[0] + a[1]+a[2]+a[3]][a[3]]%mod;

	printf("%lld", res);
	return 0;
}