#include <iostream>
using namespace std;

long long N, K, A[100009], dp[109][100009], mod = 1000000007;

int main() {
	cin >> N >> K;
	for (int i = 1; i <= N; i++) cin >> A[i];

	dp[0][0] = 1;
	for (int i = 1; i <= N; i++) {
		for (int j = 1; j <= K; j++) { dp[i - 1][j] += dp[i - 1][j - 1]; dp[i - 1][j] %= mod; }
		for (int j = 0; j <= K; j++) {
			long long R = dp[i - 1][j];
			long long L = 0; if (j > A[i]) L = dp[i - 1][j - A[i] - 1];
			dp[i][j] = (R - L + mod) % mod;
		}
	}
	cout << dp[N][K] << endl;
	return 0;
}