#include<stdio.h>
#include<stdlib.h>
#include<iostream>
#include<algorithm>
#include<set>
#include<map>
#include<string>
#include<vector>

using namespace std;

typedef long long ll;

const int MX = 105;
const int MM = 1000000007;

typedef pair<int,int> pii;

ll t[MX][MX*MX];

int add(int x, int y){
	return x+y >= MM? x+y-MM : x+y;
}

int main()
{
	int N, K;
	scanf("%d%d", &N, &K);
	t[N+1][0] = 1;
	for(int i = N; i >= 1; i--){
		for(int j = 0; j < MX*MX; j++){
			if( t[i+1][j] == 0 ) continue;
			for(int k = 0; k <= K; k++){
				if( k <= i ){
					int p = (k + j) / i;
					t[i][p + j] = add(t[i][p+j], t[i+1][j]);
				}
				else{
					t[i][j] = add(t[i][j], t[i+1][j]);
				}
			}
		}
	}
	ll m = 1;
	for(int i = 2; i <= N+1; i++){
		for(int j = 0; j < MX*MX; j++){
			t[i][j] = t[i][j] * m % MM;
		}
		if(i != N+1) m = m*(K+1) % MM;
	}
	ll ans = 0;
	for(int i = 1; i <= N; i++){
		ans = add(ans, K*(K+1)/2 * m % MM);
	}
	for(int i = 1; i <= N; i++){
		for(int j = 0; j < MX*MX; j++){
			if( t[i+1][j] == 0 ) continue;
			for(int k = 0; k <= K; k++){
				int p = (j + k) / i;
				if( k <= i ){
					ans = add(ans, MM - t[i+1][j] * p % MM);
				}
			}
		}
	}
	printf("%lld\n", ans);
}
