#include <iostream>
#include <fstream>
#include <iomanip>
#include <climits>
#include <limits>
#include <algorithm>
#include <array>
#include <vector>
#include <deque>
#include <queue>
#include <list>
#include <stack>
#include <string>
#include <functional>
#include <numeric>
#include <map>
#include <set>
#include <cstdlib>
#include <bitset>
#include <unordered_map>
#include <random>
#include <cmath>
#include <complex>
// #include "utiltime.hpp"

using namespace std;

typedef long long int ll;
typedef vector<int> vi;
typedef vector<vector<int>> vvi;
typedef pair<int, int> P;
typedef pair<ll, ll> Pll;
typedef vector<ll> vll;
typedef vector<vector<ll>> vvll;
typedef complex<double> cdouble;

const int INFL = (int)1e9;
const ll INFLL = (ll)1e18;
const double INFD = numeric_limits<double>::infinity();
const double PI = 3.14159265358979323846;
#define Loop(i, n) for(int i = 0; i < (int)(n); i++)
#define Loopll(i, n) for(ll i = 0; i < (ll)(n); i++)
#define Loop1(i, n) for(int i = 1; i <= (int)(n); i++)
#define Loopll1(i, n) for(ll i = 1; i <= (ll)(n); i++)
#define Loopr(i, n) for(int i = (int)(n) - 1; i >= 0; i--)
#define Looprll(i, n) for(ll i = (ll)(n) - 1; i >= 0; i--)
#define Loopr1(i, n) for(int i = (int)(n); i >= 1; i--)
#define Looprll1(i, n) for(ll i = (ll)(n); i >= 1; i--)
#define Foreach(buf, container) for(auto buf : container)
#define Loopdiag(i, j, h, w, sum) for(int i = ((sum) >= (h) ? (h) - 1 : (sum)), j = (sum) - i; i >= 0 && j < (w); i--, j++)
#define Loopdiagr(i, j, h, w, sum) for(int j = ((sum) >= (w) ? (w) - 1 : (sum)), i = (sum) - j; j >= 0 && i < (h); j--, i++)
#define Loopdiagsym(i, j, h, w, gap) for (int i = ((gap) >= 0 ? (gap) : 0), j = i - (gap); i < (h) && j < (w); i++, j++)
#define Loopdiagsymr(i, j, h, w, gap) for (int i = ((gap) > (h) - (w) - 1 ? (h) - 1 : (w) - 1 + (gap)), j = i - (gap); i >= 0 && j >= 0; i--, j--)
#define Loopitr(itr, container) for(auto itr = container.begin(); itr != container.end(); itr++)
#define printv(vector) Loop(extra_i, vector.size()) { cout << vector[extra_i] << " "; } cout << endl;
#define printmx(matrix) Loop(extra_i, matrix.size()) { Loop(extra_j, matrix[extra_i].size()) { cout << matrix[extra_i][extra_j] << " "; } cout << endl; }
#define quickio() ios::sync_with_stdio(false); cin.tie(0);
#define readfile(filename) ifstream in(filename); cin.rdbuf(in.rdbuf());
#define bitmanip(m,val) static_cast<bitset<(int)m>>(val)
bool nearlyeq(double x, double y) { return abs(x - y) < 1e-9; }
bool inrange(int x, int t) { return x >= 0 && x < t; }
ll rndf(double x) { return (ll)(x + (x >= 0 ? 0.5 : -0.5)); }
ll floorsqrt(double x) { ll m = (ll)sqrt(x); return m + (m * m <= (ll)(x) ? 0 : -1); }
ll ceilsqrt(double x) { ll m = (ll)sqrt(x); return m + ((ll)x <= m * m ? 0 : 1); }
ll rnddiv(ll a, ll b) { return (a / b + (a % b * 2 >= b ? 1 : 0)); }
ll ceildiv(ll a, ll b) { return (a / b + (a % b == 0 ? 0 : 1)); }
ll gcd(ll m, ll n) { if (n == 0) return m; else return gcd(n, m % n); }

/*******************************************************/

namespace mod_op {

	const ll MOD = (ll)1e9 + 7;

	class modll {
	private:
		ll val;
		inline ll modify(ll x) { ll ret = x % MOD; if (ret < 0) ret += MOD; return ret; }
		inline ll inv(ll x) {
			if (x == 0) return 1 / x;
			else if (x == 1) return 1;
			else return modify(inv(MOD % x) * modify(-MOD / x));
		}
	public:
		modll(ll init = 0) { val = modify(init); return; }
		modll(const modll& another) { val = another.val; return; }
		inline modll& operator=(const modll &another) { val = another.val; return *this; }
		inline modll operator+(const modll &x) { return modify(val + x.val); }
		inline modll operator-(const modll &x) { return modify(val - x.val); }
		inline modll operator*(const modll &x) { return modify(val * x.val); }
		inline modll operator/(const modll &x) { return modify(val * inv(x.val)); }
		inline modll& operator+=(const modll &x) { val = modify(val + x.val); return *this; }
		inline modll& operator-=(const modll &x) { val = modify(val - x.val); return *this; }
		inline modll& operator*=(const modll &x) { val = modify(val * x.val); return *this; }
		inline modll& operator/=(const modll &x) { val = modify(val * inv(x.val)); return *this; }
		inline bool operator==(const modll &x) { return val == x.val; }
		inline bool operator!=(const modll &x) { return val != x.val; }
		friend inline istream& operator >> (istream &is, modll& x) { is >> x.val; return is; }
		friend inline ostream& operator << (ostream &os, const modll& x) { os << x.val; return os; }
		ll get_val() { return val; }
	};

}

using namespace mod_op;
typedef vector<modll> vmodll;
typedef vector<vector<modll>> vvmodll;

int main() {
	int n, k; cin >> n >> k;
	vi a(n); Loop(i, n) cin >> a[i];
	vvmodll dp(n + 1, vmodll(k + 1, 0));
	dp[0][k] = 1;
	Loop1(i, n) {
		vmodll sums(k + 1);
		Loop(j, k + 1) {
			sums[j] = (j > 0 ? sums[j - 1] : 0) + dp[i - 1][j];
		}
		Loop(j, k + 1) {
			dp[i][j] = sums[min(j + a[i - 1], k)] - sums[j] + dp[i - 1][j];
		}
	}
	cout << dp[n][0] << endl;
}

Measured memory_bytes: 80256