//  ____            _                  _                       _       _
// |  _ \ _   _ ___| |_    ___ _ __   | |_ ___ _ __ ___  _ __ | | __ _| |_ ___
// | |_) | | | / __| __|  / __| '_ \  | __/ _ \ '_ ` _ \| '_ \| |/ _` | __/ _ \
// |  _ <| |_| \__ \ |_  | (__| |_) | | ||  __/ | | | | | |_) | | (_| | ||  __/
// |_| \_\\__,_|___/\__|  \___| .__/___\__\___|_| |_| |_| .__/|_|\__,_|\__\___|
//                            |_| |_____|               |_|

//                                                     _        _ _ _____  ___
//                               _ __ ___   __ _ _ __ | |_ __ _/ / |___ / / _ \
//                              | '_ ` _ \ / _` | '_ \| __/ _` | | | |_ \| | | |
//                              | | | | | | (_| | | | | || (_| | | |___) | |_| |
//                              |_| |_| |_|\__,_|_| |_|\__\__,_|_|_|____/ \___/

//https://github.com/manta1130/Competitive_Programming_Template_Rust

#[macro_use]
mod input {

    use std;
    use std::io;

    const SPLIT_DELIMITER: char = ' ';

    #[macro_export]
    #[allow(unused_macros)]
    macro_rules! input {
    ( $($x:expr ),*) => {
        {
            let temp_str = input_line_str();
            let mut split_result_iter = temp_str.split_whitespace();
                $(
                let buf_split_result = split_result_iter.next();
                let buf_split_result = buf_split_result.unwrap();
                    ($x) = buf_split_result.parse().unwrap();
                )*
        }
    };
}

    #[allow(dead_code)]
    pub fn input_line_str() -> String {
        let mut s = String::new();
        io::stdin().read_line(&mut s).unwrap();
        s.trim().to_string()
    }

    #[allow(dead_code)]
    pub fn p<T>(t: T)
    where
        T: std::fmt::Display,
    {
        println!("{}", t);
    }

    #[allow(dead_code)]
    pub fn input_vector2d<T>(line: usize) -> Vec<Vec<T>>
    where
        T: std::str::FromStr,
    {
        let mut v: Vec<Vec<T>> = Vec::new();

        for _ in 0..line {
            let vec_line = input_vector();
            v.push(vec_line);
        }
        v
    }

    #[allow(dead_code)]
    pub fn input_vector<T>() -> Vec<T>
    where
        T: std::str::FromStr,
    {
        let mut v: Vec<T> = Vec::new();

        let s = input_line_str();
        let split_result = s.split(SPLIT_DELIMITER);
        for z in split_result {
            let buf = match z.parse() {
                Ok(r) => r,
                Err(_) => panic!("Parse Error"),
            };
            v.push(buf);
        }
        v
    }

    #[allow(dead_code)]
    pub fn input_vector_row<T>(n: usize) -> Vec<T>
    where
        T: std::str::FromStr,
    {
        let mut v = Vec::with_capacity(n);
        for _ in 0..n {
            let buf = match input_line_str().parse() {
                Ok(r) => r,
                Err(_) => panic!("Parse Error"),
            };
            v.push(buf);
        }
        v
    }

    pub trait ToCharVec {
        fn to_charvec(&self) -> Vec<char>;
    }

    impl ToCharVec for String {
        fn to_charvec(&self) -> Vec<char> {
            self.to_string().chars().collect::<Vec<_>>()
        }
    }
}

mod union_find {

///素集合データ構造
pub struct UnionFind {
    v: Vec<usize>,
}

impl UnionFind {
    ///要素数nの素集合データ構造を構築する。
    pub fn new(n: usize) -> UnionFind {
        let mut v = Vec::new();
        for i in 0..n {
            v.push(i);
        }
        UnionFind { v: v }
    }

    ///親を探索する。
    pub fn find(&mut self, a: usize) -> usize {
        if a == self.v[a] {
            return a;
        }

        let buf = self.v[a];
        let parent = self.find(buf);
        self.v[a] = parent;
        parent
    }

    ///親が同じか判定する。
    pub fn same(&mut self, a: usize, b: usize) -> bool {
        self.find(a) == self.find(b)
    }

    ///結合する。
    pub fn union(&mut self, a: usize, b: usize) {
        let parent_a = self.find(a);
        let parent_b = self.find(b);
        self.v[parent_a] = parent_b;
    }
}
}

use input::*;
use union_find::*;

fn kruskal(e: &Vec<(usize, usize, usize)>, n: usize) -> usize {
    let mut uf = UnionFind::new(n);
    let mut res = 0;
    for i in e {
        let &(cost, from, to) = i;
        if uf.same(from, to) {
            continue;
        }

        res += cost;
        uf.union(from, to);
    }

    res
}
fn main() {
    let n: usize;
    input!(n);

    let mut v = vec![];
    let mut ex = vec![];

    for i in 0..n {
        let (a, b): (usize, usize);
        input!(a, b);
        v.push((a, b, i));
    }

    v.sort_by(|q, w| q.0.cmp(&w.0));

    for i in 1..n {
        ex.push((v[i].0 - v[i - 1].0, v[i].2, v[i - 1].2));
    }

    v.sort_by(|q, w| q.1.cmp(&w.1));
    for i in 1..n {
        ex.push((v[i].1 - v[i - 1].1, v[i].2, v[i - 1].2));
    }

    ex.sort();

    p(kruskal(&ex, n));
}


Measured memory_bytes: 17840