use std::io::*;

fn main() {
    let mut s: String = String::new();
    std::io::stdin().read_to_string(&mut s).ok();
    let mut itr = s.trim().split_whitespace();
    let n: f64 = itr.next().unwrap().parse().unwrap();
    let k: f64 = itr.next().unwrap().parse().unwrap();

    let mut ans = 0.0;
    let bunbo = (n + 1.0) * k;
    for i in 0..n as usize + 1 {
        ans += i as f64 * k / bunbo;
    }
    println!("{:.10}", ans);
}