#include <iostream>
#include <vector>
using namespace std;
const int maxn = 1005;
typedef long long ll;
const ll MOD = 1e9 + 7;

void subtract_module(ll &x, ll y) {
    x -= y;
    if(x < 0) {
        x += MOD;
    }
}
int main()
{
    ios_base::sync_with_stdio(false);
    int n, K;
    cin >> n >> K;

    vector<int> v(n);
    for(int i = 0; i < n; i++) {
        cin >> v[i];
    }

    vector<ll> dp(K + 1);
    dp[0] = 1;
    for(int at = 0; at < n; at++) {
        vector<ll> pref_sum(K + 1, 0);
        for(int used_candies = K; used_candies >= 0; used_candies--) {
            ll tmp = dp[used_candies];
            int L = used_candies + 1;
            int R = used_candies + min(v[at], K - used_candies);

            if(L <= R) {
                pref_sum[L] += tmp;

                if(R + 1 <= K) {
                    subtract_module(pref_sum[R + 1], tmp);
                }
            }

        }
        ll sum = 0;
        for(int i = 0; i <= K; i++) {
            sum += pref_sum[i];
            sum %= MOD;
            dp[i] += sum;
            dp[i] %= MOD;
        }
    }

    cout << dp[K] << endl;
    return 0;
}