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