#[macro_export]
macro_rules! setup {
    { mut $input:ident: SplitWhitespace $(,)? } => {
        use std::io::Read;
        let mut buf = String::new();
        std::io::stdin().read_to_string(&mut buf).ok();
        let mut $input = buf.split_whitespace();
    };
}

#[macro_export]
macro_rules! parse_next {
    ($str_iter:expr) => {
        $str_iter.next().unwrap().parse().ok().unwrap()
    };
}

fn main() {
    setup! { mut input: SplitWhitespace };

    let n: usize = parse_next!(input);
    let _k: usize = parse_next!(input);

    let ans = (|| {
        let mut expv = 0.0;
        for i in 0..=n {
            expv += (1.0 / ((n + 1) as f64)) * (i as f64);
        }
        expv
    })();

    println!("{}", ans);
}