fn main() {
	let mut s = String::new();
	std::io::stdin().read_line(&mut s).ok();
	let n: Vec<f64> = s.split_whitespace().flat_map(str::parse).collect();
	let a: f64 = n.iter().sum();
	println!("{}", (a - n[0].min(n[1].min(n[2]))) / a)
}