#define _USE_MATH_DEFINES
#include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <complex>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <limits>
#include <climits>
#include <cfloat>
#include <functional>
#include <iterator>
using namespace std;

const int MOD = 1000000007;

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

    vector<vector<int> > dp(n+1, vector<int>(k+1, 0));
    dp[0][0] = 1;
    for(int i=1; i<=n; ++i){
        int sum = 0;
        for(int j=0; j<=k; ++j){
            sum += dp[i-1][j];
            sum %= MOD;
            if(j - i >= 0){
                sum += MOD - dp[i-1][j-i];
                sum %= MOD;
            }
            dp[i][j] = sum;
        }
    }

    int ans = 0;
    for(int i=0; i<=k; ++i){
        ans += dp[n][i];
        ans %= MOD;
    }
    cout << ans << endl;

    return 0;
}