#include <bits/stdc++.h>
using namespace std;
 
int main() {
	int N, K; 
	cin >> N >> K; 
	const int P = N+1, Q = K+1, mod = 1e9+7, null = -1;
	using ivector = vector<int>;
	ivector a(P);
	for (int i = 1; i < P; ++i)
		cin >> a[i];
	vector<ivector> dp(P,ivector(Q,null));
	const function<int(int,int)> solve = [&](int n, int k) {
		// returns the number of ways to share (k) candies among the first 
		// (n) children such that the i-th child, 1 <= i <= n, gets v[i] candies,
		// where 0 <= v[i] <= a[i] and v[1]+v[2]+....+v[n] = k.
		if (n == 0 or k == 0) // base case
			return int(k == 0);
		if (dp[n][k] == null) { // recursive case 
			dp[n][k] = 0;
			for (int p = n-1, q = k, v = 0; q >= 0 and v <= a[n]; --q, ++v)
				dp[n][k] += solve(p,q), dp[n][k] %= mod; }
		return dp[n][k]; };
	cout << solve(N,K);
	return 0; }
 

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