WA,why?????

#include<bits/stdc++.h>

using namespace std;

int w(int a,int b,int c){
    if(a<=0||b<=0||c<=0){
        return 1;
    }
    else if(a>20||b>20||c>20){
        return w(20,20,20);
    }
    else if(a<b&&b<c){
        return w(a,b,c-1)+w(a,b-1,c-1)-w(a,b-1,c);
    }
    else{
        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);
    }
}
int main(){
    int a,b,c;
    while(cin>>a>>b>>c){
        if(a==-1&&b==-1&&c==-1){
            break;
        }
        else cout<<"w("<<a<<", "<<b<<", "<<c<<") = "<<w(a,b,c)<<endl;
    }

    return 0;
} 

帮个忙求求了