#include <bits/stdc++.h>
using namespace std;
const long long mod = 1e9 + 7;
long long p(long long a, long long b) {
  if (b == 0) return 1;
  long long tmp = p(a, b / 2);
  if (b % 2 == 0) return (tmp * tmp) % mod;
  return ((tmp * tmp) % mod * a) % mod;
}
long long inv(long long x) { return p(x, mod - 2); }
long long n, T;
long long t[200001];
long long m[200001];
long long fact[200001];
long long re_fact[200001];
long long res_E = 0;
long long comb(long long n, long long k) {
  if (k > n) return 0;
  long long c = ((fact[n] * re_fact[k]) % mod * re_fact[n - k]) % mod;
  return c;
}
int32_t main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  fact[0] = 1;
  for (long long i = 1; i <= 200000; i++) fact[i] = (fact[i - 1] * i) % mod;
  re_fact[200000] = inv(fact[200000]);
  for (long long i = 200000; i >= 1; i--)
    re_fact[i - 1] = (re_fact[i] * i) % mod;
  cin >> n >> T;
  long long sum_t = 0;
  long long pre_p = 1;
  for (long long i = 1; i <= n; i++) {
    cin >> t[i];
    sum_t += t[i];
    m[i] = min(T - sum_t, i);
    if (m[i] < 0) break;
    pre_p = ((2 * pre_p) % mod + comb(i - 1, m[i - 1] + 1)) % mod;
    if (m[i] != m[i - 1] + 1)
      for (long long j = m[i - 1] + 1; j > m[i]; j--)
        pre_p = ((pre_p - comb(i, j)) % mod + mod) % mod;
    res_E = (res_E + (inv(p(2, i)) * pre_p) % mod) % mod;
  }
  cout << res_E;
}
