#![allow(unused_imports, unused_macros)]

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

fn run<I: Input, O: Write>(mut kin: I, mut out: O) {
    let (a, b, c, d): (i64, i64, i64, i64) = kin.input();
    let ans = if (a - c).abs() + (b - d).abs() <= 3 || a == c || b == d { 1 } else { 2 };
    outln!(out, "{}", ans);
}

// -----------------------------------------------------------------------------
fn main() -> io::Result<()> {
    std::thread::Builder::new()
        .stack_size(1 << 26)
        .spawn(|| {
            run(
                KInput::new(io::stdin().lock()),
                io::BufWriter::new(io::stdout().lock()),
            )
        })?
        .join()
        .unwrap();
    Ok(())
}

#[macro_export]
macro_rules! out {
    ($($arg:tt)*) => { write!($($arg)*).unwrap(); }
}
#[macro_export]
macro_rules! outln {
    ($dst:expr $(, $($arg:tt)*)?) => {{
        writeln!($dst $(, $($arg)*)?).unwrap();
        if cfg!(debug_assertions) { $dst.flush().unwrap(); }
    }}
}
#[macro_export]
macro_rules! d {
    ($h:expr, $($t:expr),* $(,)?) => {
        #[cfg(debug_assertions)]
        {
            eprint!("[{}:{}] {} = {:?}", file!(), line!(), stringify!($h), $h);
            $(eprint!(", {} = {:?}", stringify!($t), $t);)*
            eprintln!();
        }
    };
    ($h:expr) => { d!($h,) };
    () => { eprintln!("[{}:{}]", file!(), line!()) }
}

pub mod kyoproio {
    use std::{
        io::prelude::*,
        iter::FromIterator,
        marker::PhantomData,
        mem::{self, MaybeUninit},
        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 collect<T: InputItem, B: FromIterator<T>>(&mut self, n: usize) -> B {
            self.iter().take(n).collect()
        }
        fn map<T: InputItem, U, F: FnMut(T) -> U, B: FromIterator<U>>(
            &mut self,
            n: usize,
            f: F,
        ) -> B {
            self.iter().take(n).map(f).collect()
        }
    }
    impl<I: Input> Input for &mut I {
        fn bytes(&mut self) -> &[u8] {
            (**self).bytes()
        }
    }
    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 n = self.src.read(&mut self.buf[self.len..]).unwrap();
            self.len += n;
            n
        }
    }
    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 {
                    unsafe {
                        let mut arr: [MaybeUninit<T>; $N] = MaybeUninit::uninit().assume_init();
                        for elem in &mut arr {
                            *elem = MaybeUninit::new(src.input());
                        }
                        mem::transmute_copy(&arr)
                    }
                }
            }
        )*}
    }
    array!(1 2 3 4 5 6 7 8);
}