poj 1579 Function Run Fun

#include <stdio.h>
#define N 21
int a,b,c,w[N][N][N];

int dp(int a,int b,int c)
{
    int i,j,k;

    if (a<=0 || b<=0 || c<=0)
    {
        return 1;
	}
    if (a>20 || b>20 || c>20)
    {
	   a = b = c = 20;
	}
    for (i = 0; i < N; i++) 
    {
        for (j = 0; j < N; j++)
        {
			for(k = 0; k < N; k++)
			{
				
            	w[i][j][k] = 1;
			}
		}
	}
    for (i = 1; i <= a; i++)
    {
		for (j = 1; j <= b; j++)
        {
			for (k = 1; k <= c; k++)
            {
				if (i < j && j < k)
                {
					w[i][j][k] = w[i][j][k-1] + w[i][j-1][k-1] - w[i][j-1][k];
				}
				else
    			{
					w[i][j][k] = w[i-1][j][k] + w[i-1][j-1][k] + w[i-1][j][k-1] - w[i-1][j-1][k-1];
				} 
			}
		}
	}
    return w[a][b][c];
}

int main()
{
    while (scanf("%d %d %d",&a, &b, &c) != EOF )
    {
		if(a == -1 && b == -1 && c== -1)
		{
			break;
		}
		else
		{
        	printf("w(%d, %d, %d) = %d\n",a, b, c, dp(a,b,c));
		}
	}
    return 0;
}