#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] = 0;
      for (int l = 0; l <= a[i]; l++)
        if (l <= j) {
          dp[i][j] += dp[i - 1][j - l];
          dp[i][j] %= mod;
        }
    }
  cout << dp[n][k];
}
