全TLE，求助

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
#include<string>
#include<cstring>
#include<cstdlib>
#include<vector>
#include<stack>
#include<deque>
#include<map>
using namespace std;
long w(long a,long b,long c)
{
	if(a>20||b>20||c>20) 
	{
		a=20;b=20;c=20;
	}
	if(a<=0||b<=0||c<=0) return 1;
	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);
}
int main()
{
	long a,b,c;
	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;
}