use std::io::{stdin, Read};

fn main() {
    let mut buf = String::new();
    stdin().read_to_string(&mut buf).unwrap();
    let mut tok = buf.split_whitespace();
    let mut get = || tok.next().unwrap();
    macro_rules! get {
        ($t:ty) => (get().parse::<$t>().unwrap());
        () => (get!(f64));
    }
    
    let r = get!();
    let d = get!();
    
    let l = (d * d - r * r).sqrt();
    
    println!("{}", l);
}