use std::cmp;
use std::io::*;
use std::str::FromStr;

fn calc(p: i32, q: i32, r: i32) -> f64 {
    let mn = cmp::min(p, cmp::min(q, r)) as f64;
    let sum = (p + q + r) as f64;

    1.0 - mn / sum
}

fn main() {
    let mut s = String::new();
    stdin().read_line(&mut s).ok();
    let mut it = s.split_whitespace().map(|n| i32::from_str(n).unwrap());
    let (p, q, r) = (it.next().unwrap(), it.next().unwrap(), it.next().unwrap());

    println!("{:.12}", calc(p, q, r));
}