#include <bits/stdc++.h>
const double pi = acos(-1.0);
const double eps = 1e-7;
using namespace std;
const long long MOD = 1e9 + 7;
const int N = 3e5 + 1;
long long bin_pow(long long x, long long n) {
  long long res = 1;
  while (n) {
    if (n & 1) res = res * x % MOD;
    n >>= 1;
    x = x * x % MOD;
  }
  return res;
}
long long add(long long x, long long y) {
  x += y;
  if (x >= MOD) x -= MOD;
  return x;
}
long long mult(long long x, long long y) { return x * y % MOD; }
long long rev_pow(long long x, long long n) { return bin_pow(x, MOD - n - 1); }
long long sub(long long x, long long y) {
  x -= y;
  if (x < 0) x += MOD;
  return x;
}
long long fact[N], rev_fact[N];
void fac(int ffrom) {
  fact[0] = 1;
  for (int i = 1; i <= ffrom; i++) fact[i] = mult(fact[i - 1], 1ll * i);
  rev_fact[ffrom] = rev_pow(fact[ffrom], 1);
  for (int i = ffrom - 1; i >= 0; i--)
    rev_fact[i] = mult(rev_fact[i + 1], 1ll * (i + 1));
}
long long C(int n, int k) {
  if (k > n || k < 0) return 0;
  return mult(mult(fact[n], rev_fact[k]), rev_fact[n - k]);
}
void solve() {
  int n;
  long long T;
  cin >> n >> T;
  fac(n + 10);
  vector<long long> t(n + 1);
  for (int i = 1; i <= n; i++) cin >> t[i];
  long long sum = 0;
  long long last_ans = 0;
  int last_id = -2;
  long long ans = 0;
  for (int i = 1; i <= n; i++) {
    sum += t[i];
    if (sum > T) break;
    int now_id;
    long long now_ans;
    if (T - sum >= i)
      now_id = i;
    else
      now_id = T - sum;
    now_ans = add(mult(last_ans, 2), C(i - 1, last_id + 1));
    now_ans = sub(now_ans, C(i, last_id + 1));
    if (now_id > last_id) {
      for (int j = max(-1, last_id) + 1; j <= now_id; j++)
        now_ans = add(now_ans, C(i, j));
    } else if (now_id < last_id) {
      for (int j = now_id + 1; j <= last_id; j++)
        now_ans = sub(now_ans, C(i, j));
    }
    ans = add(ans, mult(now_ans, rev_pow(2, i)));
    last_ans = now_ans;
    last_id = now_id;
  }
  cout << ans << endl;
}
int main() {
  ios::sync_with_stdio(NULL), cin.tie(0), cout.tie(0);
  cout.setf(ios::fixed), cout.precision(10);
  int step;
  step = 1;
  for (int i = 1; i <= step; i++) {
    solve();
  }
}
