#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,n) for (int i=a;i<n;i++)
#define per(i,a,n) for (int i=n-1;i>=a;i--)
#define pb push_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define SZ(x) ((int)(x).size())
typedef vector<int> VI;
typedef long long ll;
typedef pair<int,int> PII;
const ll mod=1000000007;
ll powmod(ll a,ll b) {ll res=1;a%=mod; assert(b>=0); for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
ll gcd(ll a,ll b) { return b?gcd(b,a%b):a;}
// head

const int N=110;
void upd(int &a,int b) { a+=b; if (a>=mod) a-=mod; }
int n,m;
int dp[N][N*N];
ll ret;
int main() {
	scanf("%d%d",&n,&m);
	dp[n][0]=1;
	per(i,0,n) rep(j,0,n*m+1) if (dp[i+1][j]>0) {
		rep(k,0,m+1) {
			if (k<=i+1&&k+j>=i+1) upd(dp[i][j+(k+j)/(i+1)],dp[i+1][j]);
			else upd(dp[i][j],dp[i+1][j]);
		}
	}
	ret=m*(m+1)/2*n*powmod(m+1,n-1)%mod;
	rep(i,0,n*m+1) {
		ret=(ret-(ll)dp[0][i]*i)%mod;
	}
	if (ret<0) ret+=mod;
	printf("%lld\n",ret);
}
