// By ksun48

#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
 
LL dp[110][11000];
 
#define MOD 1000000007
LL powmod(LL a, LL n){
    if(n == 0) return 1;
    if(n % 2) return (a*powmod(a,n-1)) % MOD;
    LL c = powmod(a, n/2);
    return (c*c) % MOD;
}
LL inv(LL a){
    return powmod(a, MOD-2);
}
 
 
int main(){
    LL n, k;
    cin >> n >> k;
    for(LL N = 0; N <= n; N++){
        for(LL a = 0; a <= k*(n-N); a++){
            dp[N][a] = 0;
            if(N == 0) continue;
            for(LL val = 0; val <= k; val++){
                LL numadd = 0;
                LL newval = val + a;
                if(val <= N){
                    numadd = (val + a) / N;
                    newval = (val + a) % N;
                }
                dp[N][a] += dp[N-1][a + numadd];
                dp[N][a] %= MOD;
                dp[N][a] += newval * powmod(k+1, N-1);
                dp[N][a] %= MOD;
            }
        }
    }
    cout << dp[n][0] << endl;
}