#include <bits/stdc++.h>
using namespace std;
# define MOD 1000000007
int main() {
	int n, k;
	cin>>n>>k;
	int arr[n];
	for(int i=0;i<n;i++){
	    cin>>arr[i];
	}
	int dp[n+1][k+1];
	dp[0][0] = 1;
	for(int i=1;i<=k;i++){
	    dp[0][i] = 0;
	}
	for(int i=1;i<=n;i++){
	    for(int j=0;j<=k;j++){
	        if(j == 0){
	            dp[i][j] = dp[i-1][j];
	        }else{
	            dp[i][j] = ((dp[i-1][j] + dp[i][j-1])%MOD - ((j-1-arr[i-1] >= 0) ? dp[i-1][j-1-arr[i-1]] : 0) + MOD)%MOD;
	        }
	    }
	}
	cout<<dp[n][k];
	return 0;
}