#include <bits/stdc++.h>
using namespace std;
const int MOD = 1e9 + 7;
int main() {
  int n, k;
  cin >> n >> k;
  vector<int> pref(k), dp(k);
  dp[0] = 1;
  for (int kid = 1; kid <= n; kid++) {
    int c;
    cin >> c;
    pref[0] = dp[0];
    dp[0] = 0;
    for (int i = 1; i <= k; i++) {
      pref[i] = (pref[i - 1] + dp[i]) % MOD;
    }
    for (int i = 0; i <= k; i++) {
      dp[i] = (pref[i] - (i - c >= 0 ? pref[i - c - 1] : 0)) % MOD;
    }
  }
  int ans = dp[k];
  if (ans < 0) ans += MOD;
  printf("%d\n", ans);
  return 0;
}
