玄关

#include <bits/stdc++.h>
using namespace std;
const int MAX_N = 21;
vector<vector<vector<int> > > memo(MAX_N, vector<vector<int> >(MAX_N, vector<int>(MAX_N, 0)));
int w(int a, int b, int c) {
    if (a <= 0 || b <= 0 || c <= 0)
        return 1;
    if (a > 20 || b > 20 || c > 20)
        return w(20, 20, 20);
    if (memo[a][b][c] != 0)
        return memo[a][b][c];
    int result;
    if (a < b && b < c)
        result = w(a, b, c-1) + w(a, b-1, c-1) - w(a, b-1, c);
    else
        result = w(a-1, b, c) + w(a-1, b-1, c) + w(a-1, b, c-1) - w(a-1, b-1, c-1);

    memo[a][b][c] = result;
    return result;
}

int main() {
    int a, b, c;
    while (scanf("%d %d %d", &a, &b, &c) == 3) {
        if (a == -1 && b == -1 && c == -1)
            break;
        int result = w(a, b, c);
        printf("w(%d, %d, %d) = %d\n", a, b, c, result);
    }

    return 0;
}