WA on subtask#1

求调

#include <iostream>
using namespace std;
long long a, b, c, f[25][25][25]; 
long long w(int a, int b, int c)
{
    if (a <= 0 or b <= 0 or c <= 0)
    {
        return 1;
    }
    else if (a > 20 or b > 20 or c > 20)
    {
        return w(20 , 20 , 20);
    }
    else if (f[a][b][c])
    {
        return f[a][b][c];
    }
    else if (a < b and b < c)
    {
        f[a][b][c] = w(a , b , c - 1) + w(a , b - 1 , c - 1) - w(a , b - 1 , c);
        return f[a][b][c];
    }
    else
    {
        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()
{
    while (true)
    {
        cin >> a >> b >> c;
        if (a == -1 and b == -1 and c == -1)
        {
            break;
        }
        cout << "w(" << a << ", " << b << ", " << c << ") = " << w(a , b , c) << endl;
    }
    return 0;
}