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

using Int = long long;
const Int M = 1000000000 + 7;

int main() {
  int n, k;
  std::cin >> n >> k;
  std::vector<std::vector<Int>> count(n + 1, std::vector<Int>(k + 1, 0));
  std::vector<std::vector<Int>> acc(n + 1, std::vector<Int>(k + 1, 0));
  count[0][0] = 1;
  for (int ni = 0; ni < n; ++ni) {
    for (int ki = 0; ki <= k; ++ki) {
      if (ki == 0) acc[ni][ki] = count[ni][0];
      else acc[ni][ki] = (acc[ni][ki - 1] + count[ni][ki]) % M;
      if (ki - ni - 1 >= 0) count[ni + 1][ki] = (M + acc[ni][ki] - acc[ni][ki - ni - 1]) % M;
      else count[ni + 1][ki] = acc[ni][ki];
    }
  }
  Int ans = 0;
  for (const auto & c : count[n]) ans = (ans + c) % M;
  std::cout << ans << std::endl;
  return 0;
}