macro_rules! read_line_to_tuple {
    ( $( $t:ty ),* ) => {{
        let mut input = String::new();
        std::io::stdin().read_line(&mut input).unwrap();
        let mut iter = input.split_whitespace();
        ( $( iter.next().unwrap().parse::<$t>().unwrap() ),* )
    }};
}

use std::mem::swap;

fn main() {
    let (mut p, mut q, mut r) = read_line_to_tuple!(f64, f64, f64);

    if p > q { swap(&mut p, &mut q); }
    if q > r { swap(&mut q, &mut r); }
    if p > q { swap(&mut p, &mut q); }

    println!("{:.10}", (q + r) / (p + q + r));
}