/**
 *   @FileName	a.cpp
 *   @Author	kanpurin
 *   @Created	2020.06.07 00:57:26
**/

#include "bits/stdc++.h" 
using namespace std; 
typedef long long ll;

constexpr int MOD = 1e9 + 7;
struct mint {
private:
    long long x;
public:
    mint(long long x = 0) :x((MOD+x)%MOD) {}
    mint(std::string &s) {
        long long z = 0;
        for (int i = 0; i < s.size(); i++) {
            z *= 10;
            z += s[i] - '0';
            z %= MOD;
        }
        this->x = z;
    }
    mint& operator+=(const mint &a) {
        if ((x += a.x) >= MOD) x -= MOD;
        return *this;
    }
    mint& operator-=(const mint &a) {
        if ((x += MOD - a.x) >= MOD) x -= MOD;
        return *this;
    }
    mint& operator*=(const mint &a) {
        (x *= a.x) %= MOD;
        return *this;
    }
    mint& operator/=(const mint &a) {
        long long n = MOD - 2;
        mint u = 1, b = a;
        while (n > 0) {
            if (n & 1) {
                u *= b;
            }
            b *= b;
            n >>= 1;
        }
        return *this *= u;
    }
    mint operator+(const mint &a) const {
        mint res(*this);
        return res += a;
    }
    mint operator-(const mint &a) const {
        mint res(*this);
        return res -= a;
    }
    mint operator*(const mint &a) const {
        mint res(*this);
        return res *= a;
    }
    mint operator/(const mint &a) const {
        mint res(*this);
        return res /= a;
    }
    friend std::ostream& operator<<(std::ostream &os, const mint &n) {
        return os << n.x;
    }
    bool operator==(const mint &a) const {
        return this->x == a.x;
    }
};
int main() {
    int n,k;cin >> n >> k;
    for (int i = 0; i < n; i++) {
        int a;cin >> a;
    }
    vector<vector<mint>> dp(n+1,vector<mint>(k+1,0));
    dp[0][0] = 1;
    for (int i = 0; i < n; i++) {
        mint t = 0;
        for (int j = 0; j <= k; j++) {
            t += dp[i][j];
            if (j >= i + 1) {
                t -= dp[i][j - i - 1];
            }
            dp[i + 1][j] = t;
        }
    }
    mint ans = 0;
    for (int i = 0; i <= k; i++) {
        ans += dp[n][i];
    }
    cout << ans << endl;
    return 0;
}