#include <bits/stdc++.h>
template <typename T, typename _T>
inline bool chk_min(T &x, const _T y) {
  return y < x ? x = y, 1 : 0;
}
template <typename T, typename _T>
inline bool chk_max(T &x, const _T y) {
  return x < y ? x = y, 1 : 0;
}
const int P = 1e9 + 7;
const int N = 2e5 + 5;
int fac[N], ifac[N];
long long s[N];
int n;
long long T;
int Pow(int a, int p) {
  int res = 1;
  for (; p > 0; p >>= 1, a = 1ll * a * a % P)
    if (p & 1) res = 1ll * res * a % P;
  return res;
}
int inv(int a) { return Pow(a, P - 2); }
int pls(int x, int y) {
  x += y;
  if (x >= P) x -= P;
  return x;
}
int nCr(int n, int m) { return 1ll * fac[n] * ifac[m] % P * ifac[n - m] % P; }
int calc(int x, long long yl, long long yr) {
  chk_max(yl, 0);
  chk_min(yr, x);
  if (yl > yr) return 0;
  int res = 0;
  for (int i = (yl), iEND = (yr); i <= iEND; ++i) res = pls(res, nCr(x, i));
  return res;
}
int main() {
  fac[0] = ifac[0] = ifac[1] = 1;
  for (int i = (1), iEND = (N - 2); i <= iEND; ++i)
    fac[i] = 1ll * fac[i - 1] * i % P;
  for (int i = (2), iEND = (N - 2); i <= iEND; ++i)
    ifac[i] = 1ll * (P - P / i) * ifac[P % i] % P;
  for (int i = (2), iEND = (N - 2); i <= iEND; ++i)
    ifac[i] = 1ll * ifac[i - 1] * ifac[i] % P;
  scanf("%d%lld", &n, &T);
  for (int i = (1), iEND = (n); i <= iEND; ++i)
    scanf("%lld", &s[i]), s[i] += s[i - 1];
  int ans = 0;
  for (int i = (1), iEND = (n - 1); i <= iEND; ++i) {
    ans = pls(ans, 1ll * i * calc(i, T - s[i + 1] + 1, T - s[i]) % P *
                       Pow(2, n - i - 1) % P);
    ans = pls(ans, 1ll * i * calc(i, T - s[i + 1], T - s[i]) % P *
                       Pow(2, n - i - 1) % P);
  }
  ans = pls(ans, 1ll * n * calc(n, 0, T - s[n]) % P);
  printf("%lld\n", 1ll * ans * inv(Pow(2, n)) % P);
  return 0;
}
