POJ Function Run Fun

#include <iostream>using namespace std;int w[21][21][21] = {0};int fun(int a,int b,int c){if(a<=0||b<=0||c<=0)return 1;else if(a<b&&b<c)return w[a][b][c-1]+w[a][b-1][c-1]-w[a][b-1][c];elsereturn 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(){for(int a = 0;a<21;a++){for(int b = 0;b<21;b++){for(int c = 0;c<21;c++){w[a][b][c] = fun(a,b,c);}}}int x = 0;int y = 0;int z = 0;while(cin>>x>>y>>z){if(x == -1&& y == -1&&z ==-1)break;else if(x< 0 || y<0||z<0)printf("w(%d, %d, %d) = %d\n", x, y, z, 1);else if(x>20 || y >20 ||z>20)printf("w(%d, %d, %d) = %d\n", x, y, z, w[20][20][20]);else printf("w(%d, %d, %d) = %d\n", x, y, z, w[x][y][z]);}}