求助！全TLE！

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