全MLE求助

#include<bits/stdc++.h>
typedef long long ll;
using namespace std;
ll fun[30][30][30];
ll w(ll a,ll b,ll 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(fun[a][b][c])return fun[a][b][c];
	else if(a<b&&b<c)return fun[a][b][c]=w(a,b,c-1)+w(a,b-1,c-1)-w(a,b-1,c);
	return fun[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(1){
		memset(fun,0,sizeof(fun));
        scanf("%lld%lld%lld",&a,&b,&c);
        if(a==-1&&b==-1&&c==-1)
            return 0;
        printf("w(%lld,%lld,%lld)=%lld\n",a,b,c,w(a,b,c));
    }
}