#[allow(unused_imports)]
use std::char::from_digit;
#[allow(unused_imports)]
use std::cmp::{max, min};
#[allow(unused_imports)]
use std::collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, VecDeque};
#[allow(unused_imports)]
use std::fs::File;
#[allow(unused_imports)]
use std::io::prelude::*;
#[allow(unused_imports)]
use std::io::{stdin, stdout, BufReader, BufWriter, Stdin, Stdout, Write};
#[allow(unused_imports)]
use std::mem::swap;
#[allow(unused_imports)]
use std::str::FromStr;
type BoxResult<T> = Result<T, Box<std::error::Error>>;

fn main() {
    let mut scanner = Scanner::new(stdin());
    let n = scanner.read::<usize>().unwrap();
    let mut points = vec![];
    let mut horizontal = vec![];
    let mut vertical = vec![];
    for i in 0..n {
        let line = scanner.read_vector::<i64>().unwrap();
        points.push((line[0], line[1]));
        horizontal.push((line[0], line[1], i));
        vertical.push((line[1], line[0], i));
    }
    horizontal.sort();
    vertical.sort();

    let mut sum = 0;
    let mut used = vec![false; n];
    let mut heap = BinaryHeap::new();
    heap.push(encode(0, 0));
    while heap.len() > 0 {
        let (crt, cost) = decode(heap.pop().unwrap());
        if used[crt] {
            continue;
        }
        sum += cost;
        used[crt] = true;
        let (x, y) = points[crt];
        let index_1 = horizontal.binary_search(&(x, y, crt)).unwrap();
        update(index_1, &horizontal, x, &mut heap);
        let index_2 = vertical.binary_search(&(y, x, crt)).unwrap();
        update(index_2, &vertical, y, &mut heap);
    }
    println!("{}", sum);
}

fn encode(p: usize, c: i64) -> (i64, usize) {
    (-c, p)
}

fn decode(item: (i64, usize)) -> (usize, i64) {
    (item.1, -item.0)
}

fn update(i: usize, arr: &[(i64, i64, usize)], val: i64, heap: &mut BinaryHeap<(i64, usize)>) {
    if i > 0 {
        let p = arr[i - 1];
        heap.push(encode(p.2, (p.0 - val).abs()));
    }
    if i < arr.len() - 1 {
        let p = arr[i + 1];
        heap.push(encode(p.2, (p.0 - val).abs()));
    }
}

#[allow(dead_code)]
struct Scanner<R> {
    reader: BufReader<R>,
    buffer: String,
}
impl<R> Scanner<R>
where
    R: Read,
{
    #[allow(dead_code)]
    fn new(inner: R) -> Scanner<R> {
        let reader = BufReader::new(inner);
        let buffer = String::new();
        Scanner {
            reader: reader,
            buffer: buffer,
        }
    }
    #[allow(dead_code)]
    fn with_capacity(capacity: usize, inner: R) -> Scanner<R> {
        let reader = BufReader::with_capacity(capacity, inner);
        let buffer = String::new();
        Scanner {
            reader: reader,
            buffer: buffer,
        }
    }
    #[allow(dead_code)]
    fn read_line(&mut self) -> BoxResult<String> {
        self.reader.read_line(&mut self.buffer)?;
        let cloned = self.buffer.trim().to_string();
        self.buffer.clear();
        Ok(cloned)
    }
    #[allow(dead_code)]
    fn read<T>(&mut self) -> BoxResult<T>
    where
        T: FromStr,
        T::Err: std::fmt::Debug,
        T::Err: std::error::Error,
        T::Err: 'static,
    {
        self.reader.read_line(&mut self.buffer)?;
        let parsed = self.buffer.trim().parse()?;
        self.buffer.clear();
        Ok(parsed)
    }
    #[allow(dead_code)]
    fn read_vector<T>(&mut self) -> BoxResult<Vec<T>>
    where
        T: FromStr,
        T::Err: std::fmt::Debug,
        T::Err: std::error::Error,
        T::Err: 'static,
    {
        self.reader.read_line(&mut self.buffer)?;
        let parsed_vec = self
            .buffer
            .trim()
            .split_whitespace()
            .map(|s| s.parse())
            .collect::<Result<Vec<_>, _>>()?;
        self.buffer.clear();
        Ok(parsed_vec)
    }
    #[allow(dead_code)]
    fn read_matrix<T>(&mut self, lines: usize) -> BoxResult<Vec<Vec<T>>>
    where
        T: FromStr,
        T::Err: std::fmt::Debug,
        T::Err: std::error::Error,
        T::Err: 'static,
    {
        let mut parsed_matrix = vec![];
        for _ in 0..lines {
            self.reader.read_line(&mut self.buffer)?;
            parsed_matrix.push(
                self.buffer
                    .trim()
                    .split_whitespace()
                    .map(|s| s.parse())
                    .collect::<Result<Vec<_>, _>>()?,
            );
            self.buffer.clear();
        }
        Ok(parsed_matrix)
    }
    #[allow(dead_code)]
    fn read_chars(&mut self) -> BoxResult<Vec<char>> {
        self.reader.read_line(&mut self.buffer)?;
        let chars = self.buffer.trim().chars().collect::<Vec<_>>();
        self.buffer.clear();
        Ok(chars)
    }
}


Measured memory_bytes: 21940