#include <iostream>
#include <algorithm>
#include <map>
#include <cassert>
using namespace std;
using i64 = long long;

constexpr int mod = int(powl(10, 9)) + 7;
vector<vector<int>> dp;

int f(int n, int k) {
  k = min(k, n*(n-1)/2);
  int &res = dp[n][k];
  if(res != -1) { return res; }
  if(n == 0 && k == 0) { return res = 1; }
  res = 0;
  if(k >= 1) {
    res += f(n, k-1);
    res %= mod;
  }
  res += f(n-1, k);
  res %= mod;
  if(k >= n) {
    res -= f(n-1, k-n);
    res %= mod;
    res += mod;
    res %= mod;
  }
  return res;
}

int main(void) {
  int n, k; scanf("%d%d", &n, &k);
  dp.assign(n+1, vector<int>(k+1, -1));
  int res = f(n, k);
  printf("%d\n", res);
  return 0;
}