#include <bits/stdc++.h>
using namespace std;
template <class T>
inline void amin(T &x, const T &y) {
  if (y < x) x = y;
}
template <class T>
inline void amax(T &x, const T &y) {
  if (x < y) x = y;
}
template <class Iter>
void rprintf(const char *fmt, Iter begin, Iter end) {
  for (bool sp = 0; begin != end; ++begin) {
    if (sp)
      putchar(' ');
    else
      sp = true;
    printf(fmt, *begin);
  }
  putchar('\n');
}
template <unsigned MOD_>
struct ModInt {
  static const unsigned MOD = MOD_;
  unsigned x;
  void undef() { x = (unsigned)-1; }
  bool isnan() const { return x == (unsigned)-1; }
  inline int geti() const { return (int)x; }
  ModInt() { x = 0; }
  ModInt(const ModInt &y) { x = y.x; }
  ModInt(int y) {
    if (y < 0 || (int)MOD <= y) y %= (int)MOD;
    if (y < 0) y += MOD;
    x = y;
  }
  ModInt(unsigned y) {
    if (MOD <= y)
      x = y % MOD;
    else
      x = y;
  }
  ModInt(long long y) {
    if (y < 0 || MOD <= y) y %= MOD;
    if (y < 0) y += MOD;
    x = y;
  }
  ModInt(unsigned long long y) {
    if (MOD <= y)
      x = y % MOD;
    else
      x = y;
  }
  ModInt &operator+=(const ModInt y) {
    if ((x += y.x) >= MOD) x -= MOD;
    return *this;
  }
  ModInt &operator-=(const ModInt y) {
    if ((x -= y.x) & (1u << 31)) x += MOD;
    return *this;
  }
  ModInt &operator*=(const ModInt y) {
    x = (unsigned long long)x * y.x % MOD;
    return *this;
  }
  ModInt &operator/=(const ModInt y) {
    x = (unsigned long long)x * y.inv().x % MOD;
    return *this;
  }
  ModInt operator-() const { return (x ? MOD - x : 0); }
  ModInt inv() const { return pow(MOD - 2); }
  ModInt pow(long long y) const {
    ModInt b = *this, r = 1;
    if (y < 0) {
      b = b.inv();
      y = -y;
    }
    for (; y; y >>= 1) {
      if (y & 1) r *= b;
      b *= b;
    }
    return r;
  }
  ModInt extgcd() const {
    unsigned a = MOD, b = x;
    int u = 0, v = 1;
    while (b) {
      int t = a / b;
      a -= t * b;
      swap(a, b);
      u -= t * v;
      swap(u, v);
    }
    if (u < 0) u += MOD;
    return ModInt(u);
  }
  friend ModInt operator+(ModInt x, const ModInt y) { return x += y; }
  friend ModInt operator-(ModInt x, const ModInt y) { return x -= y; }
  friend ModInt operator*(ModInt x, const ModInt y) { return x *= y; }
  friend ModInt operator/(ModInt x, const ModInt y) { return x *= y.inv(); }
  friend bool operator<(const ModInt x, const ModInt y) { return x.x < y.x; }
  friend bool operator==(const ModInt x, const ModInt y) { return x.x == y.x; }
  friend bool operator!=(const ModInt x, const ModInt y) { return x.x != y.x; }
};
const long long MOD = 1000000007;
int N, K;
ModInt<MOD> dp[101][10011];
ModInt<MOD> way[101][10011];
void MAIN() {
  scanf("%d%d", &N, &K);
  int LIMIT = N * K + 1;
  way[N + 1][0] = 1;
  for (int i = N; i >= 1; i--) {
    for (int a = 0, a_len = (K + 1); a < a_len; ++a) {
      if (a <= i) {
        for (int s = 0, s_len = (LIMIT); s < s_len; ++s) {
          int ns = s + (a + s) / i;
          way[i][ns] += way[i + 1][s];
          dp[i][ns] += dp[i + 1][s] + a * way[i + 1][s];
        }
      } else {
        for (int s = 0, s_len = (LIMIT); s < s_len; ++s) {
          way[i][s] += way[i + 1][s];
          dp[i][s] += dp[i + 1][s] + a * way[i + 1][s];
        }
      }
    }
  }
  ModInt<MOD> ans = 0;
  for (int s = 0, s_len = (LIMIT); s < s_len; ++s)
    ans += dp[1][s] - way[1][s] * s;
  printf("%d\n", ans.geti());
}
int main() {
  int TC = 1;
  for (int tc = 0, tc_len = (TC); tc < tc_len; ++tc) MAIN();
  return 0;
}
