c++上运行都没问题的！

#include<bits/stdc++.h>
using namespace std;
long long ans[25][25][25];
long long w(long long a,long long b,long long c){
	if(a <= 0||b<=0||c<=0) return 1;
	if(a > 20||b > 20||c > 20) return w(20,20,20);
	if(ans[a][b][c] != 0) return ans[a][b][c];
	if(a<b&&b<c){
		ans[a][b][c] = w(a,b,c-1)+w(a,b-1,c-1)-w(a,b-1,c);
		return ans[a][b][c];
	}
	ans[a][b][c] = w(a-1,b,c)+w(a-1,b-1,c)+w(a-1,b,c-1)-w(a-1,b-1,c-1);
	return ans[a][b][c];
}
int main(){
	long long a,b,c;
	while(true){
		scanf("%lld%lld%lld",&a,&b,&c);
		if(a==-1&&b==-1&&c==-1) break;
		long long ans = w(a,b,c);
		printf("w(%lld,%lld,%lld) = %lld\n",a,b,c,w(a,b,c));
	}
	return 0;
}