fn main() {
  let n: u64 = get::val();
  
  if n%2 == 1 || n == 0 {println!("0"); return}

  let mut m = n;
  while m%2 == 0 {m = m >> 1};
  let ans = if m == 1 {n-1} else {n-3};
  println!("{}", ans)
}

#[allow(dead_code)]
mod prime {
  pub fn is_prime(n: usize) -> bool {
    let sq = (n as f64).sqrt().floor() as usize;
    let p = (2..sq+1).all(|d| n%d != 0);
    p
  }

  pub fn primes(n: usize) -> Vec<usize> {
    if n < 2 {return vec![]}
    let mut ps = vec![true; n+1];
    ps[0] = false;
    ps[1] = false;
    for i in 2 .. n+1 {
      if ps[i] {
        for k in 2 .. n/i+1 {
          ps[i*k] = false;
        }
      }
    }
    ps.iter().enumerate().filter(|&(_,&p)|p).map(|(i,_)|i).collect()
  }

  pub fn factorize(n: u64) -> Vec<u64> {
    let sq = (n as f64).sqrt().floor() as u64;
    let mut fs = vec![];
    let mut x = n;
    for d in 2 .. sq+1 {
      if x == 1  {break}
      while x > 1 && x % d == 0 {
        fs.push(d);
        x /= d;
      }
    }
    if x != 1 {fs.push(x)};
    fs
  }
}

#[allow(dead_code)]
mod modulo {
  pub const MOD: u64 = 1_000_000_007;

  pub fn plus(x: u64, y: u64) -> u64 {
    (x + y) % MOD
  }

  pub fn mul(x: u64, y: u64) -> u64 {
    (x * y) % MOD
  }

  pub fn pow(x: u64, n: u64) -> u64 {
    match n {
      0 => 1,
      _ if n % 2 == 1 => mul(x, pow(x, n-1)),
      _ => {
        let q = pow(x, n>>1);
        mul(q, q)
      }
    }
  }
}

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

  pub fn val<T: FromStr>() -> T {
    let mut buf = String::new();
    stdin().read_line(&mut buf).ok();
    buf.trim().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();
    stdin().read_line(&mut buf).ok();
    let mut it = buf.trim().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();
    stdin().read_line(&mut buf).ok();
    let mut it = buf.trim().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();
    stdin().read_line(&mut buf).ok();
    buf.trim().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();
    stdin().read_line(&mut buf).ok();
    buf.trim().chars().collect()
  }
}