#include <bits/stdc++.h>
#pragma GCC optimize(2)
#pragma GCC optimize(3)
using namespace std;
template <typename _T>
inline void read(_T &f) {
  f = 0;
  _T fu = 1;
  char c = getchar();
  while (c < '0' || c > '9') {
    if (c == '-') fu = -1;
    c = getchar();
  }
  while (c >= '0' && c <= '9') {
    f = (f << 3) + (f << 1) + (c & 15);
    c = getchar();
  }
  f *= fu;
}
template <typename T>
void print(T x) {
  if (x < 0) putchar('-'), x = -x;
  if (x < 10)
    putchar(x + 48);
  else
    print(x / 10), putchar(x % 10 + 48);
}
template <typename T>
void print(T x, char t) {
  print(x);
  putchar(t);
}
const int N = 105;
double f[N][N * N], c[N][N], ans;
int a[N];
int n, x, sum;
int main() {
  read(n);
  read(x);
  f[0][0] = c[0][0] = 1;
  for (register int i = 1; i <= n; i++) {
    c[i][0] = 1;
    for (register int j = 1; j <= i; j++) {
      c[i][j] = c[i - 1][j - 1] + c[i - 1][j];
    }
  }
  for (register int i = 1; i <= n; i++) {
    read(a[i]);
    for (register int j = i - 1; j >= 0; j--) {
      for (register int k = sum; k >= 0; k--) {
        f[j + 1][k + a[i]] += f[j][k];
      }
    }
    sum += a[i];
  }
  ans = sum;
  for (register int i = 1; i <= n; i++) {
    for (register int j = 0; j <= sum; j++) {
      double val = ((double)n / i - 1) * x / 2 + x, p = (double)j / i;
      if (val <= p) ans -= (p - val) / c[n][i] * f[i][j];
    }
  }
  printf("%.9lf\n", ans);
  return 0;
}
