#include <iostream>
#include <cstring>
#include <vector>
using namespace std;
typedef long long ll;
int n, k;
int arr[100005];
// dp[k_left] --> brojot na nacini taka sto imame iskoristeno k_left candies
int dp[100005];
const int MOD = 1e9 + 7;
int main()
{
    ios_base::sync_with_stdio(false);
    cin >> n >> k;
    for(int i = 0; i < n; i++) {
        cin >> arr[i];
    }
    memset(dp, 0, sizeof dp);
    dp[0] = 1;

    for(int i = 0; i < n; i++) {
        vector<int> prefix_sum(k + 1, 0);
        for(int candies = k; candies >= 0; candies--) {
            int x = dp[candies];
            int L = candies + 1;
            int R = candies + min(arr[i], k - candies);
            if(L <= R) {
                prefix_sum[L] += x;
                prefix_sum[L] %= MOD;
                if(R + 1 <= k) {
                    prefix_sum[R + 1] -= x;
                    prefix_sum[R + 1] += MOD;
                    prefix_sum[R + 1] %= MOD;
                }
            }

        }
        int pref = 0;
        for(int j = 0; j <= k; j++) {
            pref += prefix_sum[j];
            pref %= MOD;
            dp[j] += pref;
            dp[j] %= MOD;
        }
    }
    cout << dp[k] << endl;
    return 0;
}