#include <bits/stdc++.h>
#define M 1000000007
#define fr(i,a,b) for(i=a;i<=b;i++)
using namespace std;

int main() {
	int n,k,i,j,last,first;
cin>>n>>k;
int a[n+1];
int prefix[n+1][k+1],dp[n+1][k+1];
fr(i,1,n)cin>>a[i];
fr(i,0,n){dp[i][0]=prefix[i][0]=1;}
fr(i,1,k){dp[0][i]=0;}
fr(i,1,k){prefix[0][i]=1;}
fr(i,1,n){
	 fr(j,1,k){
	 	last=j-a[i]-1>=0?prefix[i-1][j-a[i]-1]:0;
	 	first=prefix[i-1][j];
	 	dp[i][j]=(first-last+M)%M;
	 	prefix[i][j]=(prefix[i][j-1]+dp[i][j])%M;
	 }
}
cout<<dp[n][k]<<endl;
	return 0;
}