超时，求掉，感谢大佬

# include <iostream>
using namespace std;
long long a,b,c;
long long f(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 f(20,20,20);
    if(a<b&&b<c) return f(a,b,c-1)+f(a,b-1,c-1)-f(a,b-1,c);
    return f(a-1,b,c)+f(a-1,b-1,c)+f(a-1,b,c-1)-f(a-1,b-1,c-1);
}
int main(){
    while(cin>>a>>b>>c){
        if(a==-1&&b==-1&&c==-1){
            break;
        }
        cout<<"w(1, 1, 1) = "<<f(a,b,c)<<'\n';
    }
    return 0;
}