package main

import (
	"flag"
	"fmt"
	"math"
	"os"
	"regexp"
	"sort"
	"strconv"
)

var (
	inputFile = flag.String("input", "input.txt", "input filename")
	reLine    = regexp.MustCompile(`(?m)^(\d+)\s+(\d+)$`)
)

func main() {
	flag.Parse()
	input, err := os.ReadFile(*inputFile)
	if err != nil {
		panic(err)
	}

	var leftList, rightList []int
	for _, match := range reLine.FindAllStringSubmatch(string(input), -1) {
		leftNumber, err := strconv.Atoi(match[1])
		if err != nil {
			panic(err)
		}

		rightNumber, err := strconv.Atoi(match[2])
		if err != nil {
			panic(err)
		}

		leftList = append(leftList, leftNumber)
		rightList = append(rightList, rightNumber)
	}

	sort.SliceStable(leftList, func(i, j int) bool {
		return leftList[i] < leftList[j]
	})
	sort.SliceStable(rightList, func(i, j int) bool {
		return rightList[i] < rightList[j]
	})

	totalDistance := 0
	for i := 0; i < len(leftList); i++ {
		totalDistance += int(math.Abs(float64(leftList[i] - rightList[i])))
	}

	fmt.Println(totalDistance)
}