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