包AC，我老师教的，错了找我老师

#include<bits/stdc++.h>
#define ll long long
using namespace std;
ll f[25][25][25],vis[25][25][25];
ll w(ll a,ll b,ll c){
	if(a<=0||b<=0||c<=0)return 1;
	if(a>20||c>20||b>20)return w(20,20,20);;
	if(vis[a][b][c]!=0)return f[a][b][c];
	vis[a][b][c]=1;
	if(a<b&&b<c)return f[a][b][c]=w(a,b,c-1)+w(a,b-1,c-1)-w(a,b-1,c);
	return f[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);
}
int main(){
	ll a,b,c;
	while(true){
		cin>>a>>b>>c;
		if(a==-1&&b==-1&&c==-1){
			break;
		}
		cout<<"w("<<a<<", "<<b<<", "<<c<<") = "<<w(a,b,c)<<endl;
	}
	return 0;
}