#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

const long long mod = 1e9 + 7;

void to(long long &x, long long y) {
  x += y;
  if (x >= mod) x -= mod;
}

int main() {
  int n, K;
  cin >> n >> K;

  vector<long long> dp0(K + 1);
  dp0[0] = 1;

  for (int i = 0; i < n; i++) {
    vector<long long> dp1(K + 1);
    for (int j = 0; j <= K; j++) {
      for (int k = 0; k <= i && j + k <= K; k++) {
        to(dp1[j + k], dp0[j]);
      }
    }
    dp0 = dp1;
  }

  long long ans = 0;
  for (int i = 0; i <= K; i++) {
    (ans += dp0[i]) %= mod;
  }

  cout << ans << endl;
}