H. Hitoshizuku

#include <bits/stdc++.h>
using namespace std;

int main() {
    ios_base::sync_with_stdio(0), cin.tie(0);

    int N, C, mod; cin >> N >> C >> mod;

    auto modadd = [&](int &a, int b) {
        a += b;
        if (a >= mod) a -= mod;
    };

    vector dp(N+1, vector<int>(C+1, 0));
    dp[0][0] = 1;

    for (int c = C; c >= 1; --c) {
        for (int i = 0; i <= N-1; ++i) {
            for (int d = 0; d <  c; ++d) modadd(dp[i+1][c-d], dp[i][d]);
            for (int d = c; d <= C; ++d) modadd(dp[i+1][d-c], dp[i][d]);
        }
    }
    cout << dp[N][0] << "\n";

    return 0;
}