#include <bits/stdc++.h>
using namespace std;
const int MOD = 1e9 + 7;
int main() {
  int n, k;
  cin >> n >> k;
  vector<int> a(n);
  for (int i = 0; i < (n); ++i) cin >> a[i];
  vector<vector<long long>> dp(n + 1, vector<long long>(k + 1));
  for (int i = 0; i < (n + 1); ++i) {
    dp[i][0] = 1;
  }
  for (int i = 1; i < n + 1; i++) {
    for (int j = 0; j < (k); ++j) {
      if (j - a[i - 1] >= 0) {
        dp[i][j + 1] =
            (dp[i][j] + dp[i - 1][j + 1] - dp[i - 1][j - a[i - 1]]) % MOD;
      } else {
        dp[i][j + 1] = (dp[i][j] + dp[i - 1][j + 1]) % MOD;
      }
    }
  }
  cout << dp[n][k] << endl;
  return 0;
}
