为什么怎么测都不对？

#include <iostream>
using namespace std;
const int N = 23;
int f[N][N][N]; 
int w(long long a,long long  b,long long  c)
{
    if (f[a][b][c])
    {
        return f[a][b][c];
    }
    if (a <= 0 || b <= 0 || c <= 0)
    {
        f[1][1][1] = 1;
        return 1;
    }
    if (a > 20 || b > 20 || c > 20)
    {
        f[20][20][20] = w(20,20,20);
        return f[20][20][20];
    }
    if (a < b && b < c)
    {
        f[a][b][c] = w(a,b,c-1)+w(a,b-1,c-1)-w(a,b-1,c);
        return  w(a,b,c-1)+w(a,b-1,c-1)-w(a,b-1,c);
    }
    f[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);
    return f[a][b][c];
}
int main()
{
    long long a,b,c;
    while(true)
    {
        cin >> a >> b >> c;
        if(a == -1 && b == -1 && c == -1)
            break;
        cout << "w(" << a << ", " << b << ", " << c << ") = ";
        cout << w(a, b, c) << endl;
     }
    return 0;
}

自我感觉良好