use std::io::{BufRead, Write};

fn main() {
    let stdin = std::io::stdin();
    let stdout = std::io::stdout();
    let mut reader = std::io::BufReader::new(stdin.lock());
    let mut writer = std::io::BufWriter::new(stdout.lock());

    let p: f64 = {
        let mut buf = String::new();
        reader.read_line(&mut buf).unwrap();
        buf.trim_end().parse().unwrap()
    };

    let mut ans: f64 = 0.0;
    let mut r: f64 = 1.0;

    for i in 1..100000 {
        r *= p;
        ans += (i as f64) * r * (1.0 - p);
    }

    writeln!(writer, "{:.10}", ans).unwrap();
}