#include <bits/stdc++.h>
using namespace std;
inline void du(long long &d) {
  char t = getchar();
  bool mark = false;
  for (; t < '0' || t > '9'; t = getchar())
    if (t == '-') mark = !mark;
  for (d = 0; t >= '0' && t <= '9'; t = getchar()) d = d * 10 + t - '0';
  if (mark) d = -d;
}
const int maxn = 2e5 + 100;
const long long Mod = 1e9 + 7;
long long a[maxn];
long long sum[maxn];
long long fact[maxn], inv[maxn];
long long Montgemery(long long a, long long b, long long c) {
  long long ans = 1;
  while (b) {
    if (b & 1) ans = ans * a % c;
    a = a * a % c;
    b >>= 1;
  }
  return ans;
}
long long C(long long n, long long m) {
  return (m > n) ? 0 : fact[n] * inv[m] % Mod * inv[n - m] % Mod;
}
int main() {
  long long n, T;
  du(n);
  du(T);
  fact[0] = inv[0] = 1;
  for (int i = 1; i <= n; i++) {
    du(a[i]);
    sum[i] = sum[i - 1] + a[i];
    fact[i] = fact[i - 1] * i % Mod;
    inv[i] = inv[i - 1] * Montgemery(i, Mod - 2, Mod) % Mod;
  }
  long long ans = 0, presum = 1;
  long long M1 = 0, M2;
  long long i, j;
  for (i = 1; i <= n; i++) {
    if (sum[i] > T) break;
    ans = ans * 2 % Mod;
    M2 = min(T - sum[i], i);
    if (sum[i] + i <= T) {
      presum = presum * 2 % Mod;
      ans = (ans + presum) % Mod;
      M1 = M2;
      continue;
    }
    for (j = M1; j >= M2; j--) presum = (presum + Mod - C(i - 1, j)) % Mod;
    presum = presum * 2 % Mod;
    presum = (presum + C(i - 1, M2)) % Mod;
    ans = (ans + presum) % Mod;
    M1 = M2;
  }
  long long temp = Montgemery(2, i - 1, Mod);
  ans = ans * Montgemery(temp, Mod - 2, Mod) % Mod;
  cout << ans;
}
