#include <iostream>
#include <algorithm>
#include <iomanip>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <numeric>
#include <bitset>
#include <cmath>

static const int MOD = 1000000007;
using ll = long long;
using u32 = uint32_t;
using namespace std;

template<class T> constexpr T INF = ::numeric_limits<T>::max() / 32 * 15 + 208;

template<ll M = 1000000007>
struct modint{
    ll val;
    modint(): val(0){}
    template<typename T>
    explicit modint(T t){val = t%M; if(val < 0) val += M;}

    modint pow(ll k){
        modint res(1), x(val);
        while(k){
            if(k&1) res *= x;
            x *= x;
            k >>= 1;
        }
        return res;
    }
    template<typename T>
    modint& operator=(T a){ val = a%M; if(val < 0) val += M; return *this; }
    modint inv() {return pow(M-2);}
    modint& operator+=(modint a){ val += a.val; if(val >= M) val -= M; return *this;}
    modint& operator-=(modint a){ val += M-a.val; if(val >= M) val -= M; return *this;}
    modint& operator*=(modint a){ val = 1LL*val*a.val%M; return *this;}
    modint& operator/=(modint a){ return (*this) *= a.inv();}
    modint operator+(modint a) const {return modint(val) +=a;}
    modint operator-(modint a) const {return modint(val) -=a;}
    modint operator*(modint a) const {return modint(val) *=a;}
    modint operator/(modint a) const {return modint(val) /=a;}
    modint operator-(){ return modint(-val);}
    bool operator==(const modint a) const {return val == a.val;}
    bool operator!=(const modint a) const {return val != a.val;}
    bool operator<(const modint a) const {return val < a.val;}
};

using mint = modint<MOD>;

int main() {
    int n, k;
    cin >> n >> k;
    vector<mint> dp(k+1, mint(1));
    for (int i = 1; i <= n; ++i) {
        for (int j = k-i; j >= 0; --j) {
            dp[j+i] -= dp[j];
        }
        for (int j = 0; j < k; ++j) {
            dp[j+1] += dp[j];
        }
    }
    cout << dp.back().val << "\n";
    return 0;
}