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