#include <bits/stdc++.h>
using namespace std;
const int twx = 2e5 + 100;
const int MOD = 1000000007;
long long l, r;
long long S;
long long t[twx];
long long c[twx];
long long fc[twx];
long long n, m;
long long z;
long long ans;
long long asd1, asd2;
long long i, j;
long long read() {
  long long sum = 0;
  long long flag = 1;
  char c = getchar();
  while (c < '0' || c > '9') {
    if (c == '-') {
      flag = -1;
    }
    c = getchar();
  }
  while (c >= '0' && c <= '9') {
    sum = ((sum * 10) + c - '0');
    c = getchar();
  }
  return sum * flag;
}
void PLUS(long long &a, long long b) {
  a += b;
  a -= a > MOD ? MOD : 0;
}
int POW(int z, int k) {
  int qwe = 1;
  for (; k; z = (long long)z * z % MOD, k >>= 1) {
    if (k & 1) {
      qwe = (long long)qwe * z % MOD;
    }
  }
  return qwe;
}
long long C(long long n, long long m) {
  if (m < 0 || m > n) {
    return 0;
  }
  return (long long)c[n] * fc[m] % MOD * fc[n - m] % MOD;
}
void init() {
  n = read();
  m = read();
  for (i = 1; i <= n; i++) {
    t[i] = read();
  }
  for (c[0] = i = 1; i <= n; i++) {
    c[i] = (long long)c[i - 1] * i % MOD;
  }
  for (fc[n] = POW(c[n], MOD - 2), i = n; i; --i) {
    fc[i - 1] = (long long)fc[i] * i % MOD;
  }
  asd2 = POW(2, MOD - 2);
  asd1 = 1;
  for (i = 1; i <= n; i++) {
    z = 0;
    asd1 = (long long)asd1 * asd2 % MOD;
    S += t[i];
    r = min(m - S, (long long)i);
    l = m - S - t[i + 1];
    if (i == n) {
      l = -1;
    }
    z = 0;
    for (j = max(l + 1, (long long)0); j <= r; j++) {
      PLUS(z, C(i, j));
    }
    if (l >= 0) {
      PLUS(z, (long long)C(i, l) * asd2 % MOD);
    }
    z = (long long)z * asd1 % MOD * i % MOD;
    PLUS(ans, z);
  }
  printf("%lld\n", ans);
}
int main() {
  init();
  return 0;
}
