#include <bits/stdc++.h>
using namespace std;
int n, k;
long long dp[110][100010];
long long MOD = 1000000007;
int main() {
  cin >> n >> k;
  long long a[n];
  for (int i = 0; i < n; ++i) cin >> a[i];
  for (int i = 0; i <= n; ++i) dp[i][0] = 1;
  for (int i = 1; i <= n; ++i) {
    for (int j = 1; j <= k; ++j) {
      dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
      if (j - a[i - 1] - 1 >= 0) {
        dp[i][j] = dp[i][j] - dp[i - 1][j - a[i - 1] - 1];
        if (dp[i][j] > MOD) dp[i][j] -= MOD;
      }
    }
  }
  cout << dp[n][k] << endl;
  return 0;
}
