#include <bits/stdc++.h>
using namespace std;

int n, k, a[100010];
long long dp[110][100010], mod = 1e9+7;

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);
	cin >> n >> k;
	for(int i=0; i<n; ++i) cin >> a[i+1];
	dp[0][0] = 1;
	for(int i=1; i<=n; ++i){
		for(int j=0; j<=k; ++j){
			dp[i][j] = dp[i-1][j-min(a[i], j)] - dp[i-1][j+1];
			dp[i][j] %= mod;
			if(dp[i][j] < 0) dp[i][j] += mod;
		}
		for(int j=k-1; j>=0; --j){
			dp[i][j] += dp[i][j+1];
			dp[i][j] %= mod;
		}
	}
	cout << dp[n][k] << "\n";
}