poj1579--Function Run Fun

#include <stdio.h>
#include <string.h>
int vis[21][21][21];

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(vis[a][b][c] > 0)
return vis[a][b][c];
else if( (a < b) && ( b < c ) )
return vis[a][b][c]=w(a,b,c-1) + w(a,b-1,c-1) - w(a,b-1,c);
else
return vis[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(void)
{
int a,b,c;
while(1)
{
scanf("%d %d %d",&a,&b,&c);
if(a==-1 && b==-1 && c==-1) break;
memset(vis,0,sizeof(vis));
printf("w(%d, %d, %d) = %d\n",a,b,c,w(a,b,c));
}
return 0;
}