#ifndef LOCAL
#pragma GCC optimize "-O3"
#endif
#include <bits/stdc++.h>

typedef long long ll;
typedef long long llong;
typedef long double ld;
typedef unsigned long long ull;

using namespace std;

const ll MOD = 1e9 + 7;
ll pw(ll a, ll b) {
	ll ans = 1; while (b) {
		while (!(b & 1)) b >>= 1, a = (a * a) % MOD;
		ans = (ans * a) % MOD, --b;
	} return ans;
}

const int MX = 6000;

int n, k;
ll dp[110][MX];

void add(ll &a, ll b) {
	a += b;
	if (a >= MOD)
		a -= MOD;
}

int main() {
	cin >> n >> k;
	dp[n + 1][0] = 1;
	for (int i = n; i >= 1; --i) {
		for (int j = 0; j < MX; ++j) {
			if (dp[i + 1][j] == 0)
				continue;
			for (int l = 0; l <= k; ++l) {
				if (l > i) {
					add(dp[i][j], dp[i + 1][j]);
				}
				else  {
					add(dp[i][j + (j + l) / i], dp[i + 1][j]);
				}
			}
		}
	}
	ll ans = n * pw(k + 1, n) % MOD * k % MOD * (MOD / 2 + 1) % MOD;
	for (int i = 0; i < MX; ++i)
		ans = (ans - i * dp[1][i] % MOD + MOD) % MOD;
	cout << ans << "\n";
	return 0;
}


