fn main() {
  let n = get::val::<usize>();
  let k = get::val::<usize>();

  let t = Time::new();
  let mut rand = XorShift::new();

  let mut count = 0;
  let mut win = 0;
  while t.elapsed() < 4.9 {
    let taro: u64 = (0..n-k).map(|_|rand.from_to(1,6)).sum::<u64>() + (0..k).map(|_|rand.from_to(4,6)).sum::<u64>();
    let jiro: u64 = (0..n).map(|_|rand.from_to(1,6)).sum::<u64>();
    if taro > jiro {win += 1}
    count += 1
  }

  println!("{}", win as f64 / count as f64)
}

use std::time::*;
struct Time {
  start: Instant
}

#[allow(dead_code)]
impl Time {
  fn new() -> Time {
    Time {start: Instant::now()}
  }

  fn elapsed(&self) -> f64 {
    let sec = self.start.elapsed().as_secs() as f64;
    let nano = self.start.elapsed().subsec_nanos() as f64 / 1000000000.0;
    sec + nano
  }
}

#[derive(Copy, Clone)]
struct XorShift {
  state1: u64,
  state2: u64
}

#[allow(dead_code)]
impl XorShift {
  fn new() -> XorShift {
    use std::time::*;
    let start = Instant::now();
    let seed1 = start.elapsed().subsec_nanos() as u64;
    let seed2 = start.elapsed().subsec_nanos() as u64;
    XorShift {state1: seed1, state2: seed2}
  }

  fn next(&mut self) -> u64 {
    let mut s1 = self.state2;
    let mut s2 = self.state1;
    s1 = s1 ^ (s1 >> 26);
    s2 = s2 ^ (s2 << 23);
    s2 = s2 ^ (s2 >> 17);
    self.state1 = self.state2;
    self.state2 = s1 ^ s2;
    (self.state1 >> 1) + (self.state2 >> 1)
  }

  fn from_to(&mut self, from: u64, to: u64) -> u64 {
    self.next() % (to - from + 1) + from
  }
}

#[allow(dead_code)]
mod get {
  use std::io::*;
  use std::str::*;

  pub fn val<T: FromStr>() -> T {
    let mut buf = String::new();
    let s = stdin();
    s.lock().read_line(&mut buf).ok();
    buf.trim_right().parse::<T>().ok().unwrap()
  }

  pub fn vals<T: FromStr>(n: usize) -> Vec<T> {
    let mut vec: Vec<T> = vec![];
    for _ in 0 .. n {
      vec.push(val());
    }
    vec
  }

  pub fn tuple<T1: FromStr, T2: FromStr>() -> (T1, T2) {
    let mut buf = String::new();
    let s = stdin();
    s.lock().read_line(&mut buf).ok();
    let mut it = buf.trim_right().split_whitespace();
    let x = it.next().unwrap().parse::<T1>().ok().unwrap();
    let y = it.next().unwrap().parse::<T2>().ok().unwrap();
    (x, y)
  }

  pub fn tuples<T1: FromStr, T2: FromStr>(n: usize) -> Vec<(T1, T2)> {
    let mut vec: Vec<(T1, T2)> = vec![];
    for _ in 0 .. n {
      vec.push(tuple());
    }
    vec
  }

  pub fn tuple3<T1: FromStr, T2: FromStr, T3: FromStr>() -> (T1, T2, T3) {
    let mut buf = String::new();
    let s = stdin();
    s.lock().read_line(&mut buf).ok();
    let mut it = buf.trim_right().split_whitespace();
    let x = it.next().unwrap().parse::<T1>().ok().unwrap();
    let y = it.next().unwrap().parse::<T2>().ok().unwrap();
    let z = it.next().unwrap().parse::<T3>().ok().unwrap();
    (x, y, z)
  }

  pub fn tuple3s<T1: FromStr, T2: FromStr, T3: FromStr>(n: usize) -> Vec<(T1, T2, T3)> {
    let mut vec: Vec<(T1, T2, T3)> = vec![];
    for _ in 0 .. n {
      vec.push(tuple3());
    }
    vec
  }

  pub fn list<T: FromStr>() -> Vec<T> {
    let mut buf = String::new();
    let s = stdin();
    s.lock().read_line(&mut buf).ok();
    buf.trim_right().split_whitespace().map(|t| t.parse::<T>().ok().unwrap()).collect()
  }

  pub fn lists<T: FromStr>(h: usize) -> Vec<Vec<T>> {
    let mut mat: Vec<Vec<T>> = vec![];
    for _ in 0 .. h {
      mat.push(list());
    }
    mat
  }

  pub fn chars() -> Vec<char> {
    let mut buf = String::new();
    let s = stdin();
    s.lock().read_line(&mut buf).ok();
    buf.trim_right().chars().collect()
  }
}