fn main() {
    let mut pqr = String::new();
    std::io::stdin().read_line(&mut pqr).ok();
    let mut pqr: Vec<usize> = pqr.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    pqr.sort();
    let p = pqr[0];
    let q = pqr[1];
    let r = pqr[2];

    if p == 0 {
        println!("1.0");
        return;
    }
    let denom = p+q+r;
    let num = q + r;
    println!("{}", num as f64 / denom as f64);
}