#![allow(unused_imports, unused_macros)]

use kyoproio::*;
use std::{
    collections::*,
    io::{self, prelude::*},
    iter,
    mem::{replace, swap},
};

fn run<I: Input, O: Write>(mut kin: I, out: O) {
    let mut out = KOutput::new(out);

    let [a, b, c, d, e, f]: [f64; 6] = kin.input();
    // ax^2 + by^2 + cx + dy + e = f
    // u((x - s)^2 + (y - t)^2) = ur^2
    // u(x^2 - 2sx + s^2 + y^2 - 2ty + t^2) = ur^2
    // u = a = b
    // s = -c / 2u
    // t = -d / 2u
    // u(r^2 - s^2 - t^2) = f - e
    // r^2 = (f - e + (c ^ 2 + d ^ 2) / 4a) / a
    assert_eq!(a, b);
    let r2 = (f - e + (c * c + d * d) / (4. * a)) / a;
    let r = r2.sqrt();
    outln!(out, r);
}

// -----------------------------------------------------------------------------
fn main() -> io::Result<()> {
    std::thread::Builder::new()
        .stack_size(64 * 1024 * 1024)
        .spawn(|| {
            run(
                KInput::new(io::stdin().lock()),
                io::BufWriter::new(io::stdout().lock()),
            )
        })?
        .join()
        .unwrap();
    Ok(())
}

// -----------------------------------------------------------------------------
pub mod kyoproio {
    use std::{
        io::prelude::*,
        iter::FromIterator,
        marker::PhantomData,
        mem::{self, MaybeUninit},
        ptr, slice, str,
    };

    pub trait Input {
        fn bytes(&mut self) -> &[u8];
        fn str(&mut self) -> &str {
            str::from_utf8(self.bytes()).unwrap()
        }
        fn input<T: InputItem>(&mut self) -> T {
            T::input(self)
        }
        fn iter<T: InputItem>(&mut self) -> Iter<T, Self> {
            Iter(self, PhantomData)
        }
        fn seq<T: InputItem, B: FromIterator<T>>(&mut self, n: usize) -> B {
            self.iter().take(n).collect()
        }
    }
    pub struct KInput<R> {
        src: R,
        buf: Vec<u8>,
        pos: usize,
        len: usize,
    }
    impl<R: Read> KInput<R> {
        pub fn new(src: R) -> Self {
            Self {
                src,
                buf: vec![0; 1 << 16],
                pos: 0,
                len: 0,
            }
        }
        fn read(&mut self) -> usize {
            if self.pos > 0 {
                self.buf.copy_within(self.pos..self.len, 0);
                self.len -= self.pos;
                self.pos = 0;
            } else if self.len >= self.buf.len() {
                self.buf.resize(2 * self.buf.len(), 0);
            }
            let read = self.src.read(&mut self.buf[self.len..]).unwrap();
            self.len += read;
            read
        }
    }
    impl<R: Read> Input for KInput<R> {
        fn bytes(&mut self) -> &[u8] {
            loop {
                while let Some(d) = self.buf[self.pos..self.len]
                    .iter()
                    .position(u8::is_ascii_whitespace)
                {
                    let p = self.pos;
                    self.pos += d + 1;
                    if d > 0 {
                        return &self.buf[p..p + d];
                    }
                }
                if self.read() == 0 {
                    return &self.buf[mem::replace(&mut self.pos, self.len)..self.len];
                }
            }
        }
    }
    pub struct Iter<'a, T, I: ?Sized>(&'a mut I, PhantomData<*const T>);
    impl<'a, T: InputItem, I: Input + ?Sized> Iterator for Iter<'a, T, I> {
        type Item = T;
        fn next(&mut self) -> Option<T> {
            Some(self.0.input())
        }
        fn size_hint(&self) -> (usize, Option<usize>) {
            (!0, None)
        }
    }
    pub trait InputItem: Sized {
        fn input<I: Input + ?Sized>(src: &mut I) -> Self;
    }
    impl InputItem for Vec<u8> {
        fn input<I: Input + ?Sized>(src: &mut I) -> Self {
            src.bytes().to_owned()
        }
    }
    macro_rules! from_str {
        { $($T:ty)* } => {
            $(impl InputItem for $T {
                fn input<I: Input + ?Sized>(src: &mut I) -> Self {
                    src.str().parse::<$T>().unwrap()
                }
            })*
        }
    }
    from_str! { String char bool f32 f64 }
    macro_rules! parse_int {
        { $($I:ty: $U:ty)* } => {
            $(impl InputItem for $I {
                fn input<I: Input + ?Sized>(src: &mut I) -> Self {
                    let f = |s: &[u8]| s.iter().fold(0, |x, b| 10 * x + (b & 0xf) as $I);
                    let s = src.bytes();
                    if let Some((&b'-', t)) = s.split_first() { -f(t) } else { f(s) }
                }
            }
            impl InputItem for $U {
                fn input<I: Input + ?Sized>(src: &mut I) -> Self {
                    src.bytes().iter().fold(0, |x, b| 10 * x + (b & 0xf) as $U)
                }
            })*
        };
    }
    parse_int! { isize:usize i8:u8 i16:u16 i32:u32 i64:u64 i128:u128 }
    macro_rules! tuple {
        ($H:ident $($T:ident)*) => {
            impl<$H: InputItem, $($T: InputItem),*> InputItem for ($H, $($T),*) {
                fn input<I: Input + ?Sized>(src: &mut I) -> Self {
                    ($H::input(src), $($T::input(src)),*)
                }
            }
            tuple!($($T)*);
        };
        () => {}
    }
    tuple!(A B C D E F G);
    macro_rules! array {
        { $($N:literal)* } => {
            $(impl<T: InputItem> InputItem for [T; $N] {
                fn input<I: Input + ?Sized>(src: &mut I) -> Self {
                    let mut arr = MaybeUninit::uninit();
                    let ptr = arr.as_mut_ptr() as *mut T;
                    unsafe {
                        for i in 0..$N {
                            ptr.add(i).write(src.input());
                        }
                        arr.assume_init()
                    }
                }
            })*
        };
    }
    array! { 1 2 3 4 5 6 7 8 }
    pub struct KOutput<W: Write> {
        dest: W,
        delim: bool,
    }
    impl<W: Write> KOutput<W> {
        pub fn new(dest: W) -> Self {
            Self { dest, delim: false }
        }
        pub fn bytes(&mut self, s: &[u8]) {
            self.dest.write_all(s).unwrap();
        }
        pub fn byte(&mut self, b: u8) {
            self.bytes(slice::from_ref(&b));
        }
        pub fn output<T: OutputItem>(&mut self, x: T) {
            if self.delim {
                self.byte(b' ');
            }
            self.delim = true;
            x.output(self);
        }
        pub fn ln(&mut self) {
            self.delim = false;
            self.byte(b'\n');
            self.flush_debug();
        }
        pub fn inner(&mut self) -> &mut W {
            &mut self.dest
        }
        pub fn seq<T: OutputItem, I: IntoIterator<Item = T>>(&mut self, iter: I) {
            for x in iter.into_iter() {
                self.output(x);
            }
        }
        pub fn flush(&mut self) {
            self.dest.flush().unwrap();
        }
        pub fn flush_debug(&mut self) {
            if cfg!(debug_assertions) {
                self.flush();
            }
        }
    }
    pub trait OutputItem {
        fn output<W: Write>(self, dest: &mut KOutput<W>);
    }
    impl OutputItem for &str {
        fn output<W: Write>(self, dest: &mut KOutput<W>) {
            dest.bytes(self.as_bytes());
        }
    }
    impl OutputItem for char {
        fn output<W: Write>(self, dest: &mut KOutput<W>) {
            self.encode_utf8(&mut [0; 4]).output(dest);
        }
    }
    macro_rules! output_fmt {
        ($($T:ty)*) => {
            $(impl OutputItem for $T {
                fn output<W: Write>(self, dest: &mut KOutput<W>) {
                    write!(dest.inner(), "{}", self).unwrap();
                }
            })*
        }
    }
    output_fmt!(f32 f64);
    macro_rules! output_int {
        ($conv:ident; $U:ty; $($T:ty)*) => {
            $(impl OutputItem for $T {
                fn output<W: Write>(self, dest: &mut KOutput<W>) {
                    let mut buf = MaybeUninit::<[u8; 20]>::uninit();
                    unsafe {
                        let ptr = buf.as_mut_ptr() as *mut u8;
                        let ofs = $conv(self as $U, ptr, 20);
                        dest.bytes(slice::from_raw_parts(ptr.add(ofs), 20 - ofs));
                    }
                }
            }
            impl OutputItem for &$T {
                fn output<W: Write>(self, dest: &mut KOutput<W>) {
                    (*self).output(dest);
                }
            })*
        };
    }
    output_int!(i64_to_bytes; i64; isize i8 i16 i32 i64);
    output_int!(u64_to_bytes; u64; usize u8 u16 u32 u64);
    static DIGITS_LUT: &[u8; 200] = b"0001020304050607080910111213141516171819\
        2021222324252627282930313233343536373839\
        4041424344454647484950515253545556575859\
        6061626364656667686970717273747576777879\
        8081828384858687888990919293949596979899";
    unsafe fn i64_to_bytes(x: i64, buf: *mut u8, len: usize) -> usize {
        let (neg, x) = if x < 0 { (true, -x) } else { (false, x) };
        let mut i = u64_to_bytes(x as u64, buf, len);
        if neg {
            i -= 1;
            *buf.add(i) = b'-';
        }
        i
    }
    unsafe fn u64_to_bytes(mut x: u64, buf: *mut u8, len: usize) -> usize {
        let lut = DIGITS_LUT.as_ptr();
        let mut i = len;
        let mut two = |x| {
            i -= 2;
            ptr::copy_nonoverlapping(lut.add(2 * x), buf.add(i), 2);
        };
        while x >= 10000 {
            let rem = (x % 10000) as usize;
            two(rem % 100);
            two(rem / 100);
            x /= 10000;
        }
        let mut x = x as usize;
        if x >= 100 {
            two(x % 100);
            x /= 100;
        }
        if x >= 10 {
            two(x);
        } else {
            i -= 1;
            *buf.add(i) = x as u8 + b'0';
        }
        i
    }
    #[macro_export]
    macro_rules! out {
        ($out:expr, $($args:expr),*) => {{ $($out.output($args);)* }};
    }
    #[macro_export]
    macro_rules! outln {
        ($out:expr) => { $out.ln(); };
        ($out:expr, $($args:expr),*) => {{
            out!($out, $($args),*);
            outln!($out);
        }}
    }
    #[macro_export]
    macro_rules! kdbg {
        ($($v:expr),*) => {
            if cfg!(debug_assertions) { dbg!($($v),*) } else { ($($v),*) }
        }
    }
}