/*********************
*  Author: xuziyuan  * 
*********************/

#include <bits/stdc++.h>

#define rt0 return 0
#define rep(i,n) for(int i=0;i<n;i++)
#define repn(i,n) for(int i=1;i<=n;i++)
#define replet(c) for(char c='a';c<='z';c++) 
#define LL long long
#define pii pair <int,int>
#define pb push_back
#define fi first
#define se second
#define mpr make_pair
#define sqr(a) ((a)*(a))

using namespace std;

const LL MOD=1e9+7;

LL n,t,dp[110][10010],all=1,ans=0;

int main()
{
	cin>>n>>t;
	rep(i,n-1) all=all*(t+1)%MOD;
	all=all*(t+1)*t/2*n%MOD;
	dp[n][0]=1;
	for(int i=n;i>0;i--)
	{
		rep(j,10005)
		{
			rep(k,t+1)
			{
				if(dp[i][j]==0) continue;
				if(k<=i) dp[i-1][j+(j+k)/i]=(dp[i-1][j+(j+k)/i]+dp[i][j])%MOD;
				else dp[i-1][j]=(dp[i-1][j]+dp[i][j])%MOD;
			}
		}
	}
	repn(i,10003) ans=(ans+i*dp[0][i])%MOD;
	cout<<(all-ans+MOD)%MOD<<endl;
	rt0;
}