#include <bits/stdc++.h>
#pragma GCC optimize("O3")
using namespace std;
using ll = long long;
using P = pair<int, int>;
using T = tuple<int, int, int>;
template <class T>
inline T chmax(T &a, const T b) {
  return a = (a < b) ? b : a;
}
template <class T>
inline T chmin(T &a, const T b) {
  return a = (a > b) ? b : a;
}
constexpr int MOD = 1e9 + 7;
constexpr int inf = 1e9;
constexpr long long INF = 1e18;
int dx[] = {1, 0, -1, 0};
int dy[] = {0, 1, 0, -1};
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int n, k;
  cin >> n >> k;
  vector<int> a(n);
  for (int i = 0; i < n; i++) cin >> a[i];
  vector<vector<ll>> dp(n + 1, vector<ll>(k + 1, 0));
  dp[0][0] = 1;
  for (int i = 0; i < n; i++) {
    vector<ll> dpsum(k + 2, 0);
    for (int j = 0; j <= k; j++) {
      dpsum[j + 1] = dpsum[j] + dp[i][j];
      dpsum[j + 1] %= MOD;
    }
    for (int cur = 0; cur <= k; cur++) {
      dp[i + 1][cur] += dpsum[cur + 1] - dpsum[max(0, cur - a[i])];
      dp[i + 1][cur] %= MOD;
    }
  }
  cout << dp[n][k] << endl;
  return 0;
}
