#include <bits/stdc++.h>
using namespace std;
long long dp[110][100010],sum[100010];
const int MAXN=1e9+7;
int n,k,a[100010];
int main(){
	cin>>n>>k;
	for(int i=1;i<=n;++i){
		cin>>a[i];
		dp[i][0]=1;
	}
	dp[0][0]=1;
	for(int i=1;i<=n;++i){
		for(int j=1;j<=k+1;++j){
			sum[j]=sum[j-1]+dp[i-1][j-1];
			sum[j]%=MAXN;
		}
		for(int j=1;j<=k;++j){
			dp[i][j]=sum[j+1]-sum[max(0,j-a[i])]+MAXN;
			dp[i][j]%=MAXN;
		}
	}
	/*for(int i=1;i<=n;++i){
		for(int j=0;j<=k;++j){
			cout<<dp[i][j]<<" ";
		}
		cout<<endl;
	}*/
	cout<<dp[n][k]%MAXN<<endl;
	return 0;
}
