#include <iostream>
using namespace std;

int main(){
    int N, K;
    cin >> N >> K;
    long array_patterns[N + 1][N * (N + 1) / 2 + 1]; // now_array_size, now_inversion_number
    for(int i = 0; i <= N * (N + 1) / 2; i++){
        array_patterns[N][i] = (i <= K);
    }
    for(int i = N - 1; i >= 0; i--){
        for(int j = 0; j <= i * (i + 1) / 2; j++){
            long ans = 0;
            for(int k = 0; k <= i; k++){
                ans += array_patterns[i + 1][j + k];
                ans %= long(1e9 + 7);
            }
            array_patterns[i][j] = ans;
        }
    }
    cout << array_patterns[0][0] << endl;
}