package main

import (
    "fmt"
    "os"
    "strings"
    "strconv"
    "sort"
)

func check(e error) {
    if e != nil {
        panic(e)
    }
}

func count_sorted(list []int, elem int) int {
    counter := 0
    for i := range list {
        if list[i] == elem {
            counter++
        } else if counter > 0 {
            break
        }
    }
    return counter
}

func main() {
    // read in file as lines
    dat, err := os.ReadFile("data.txt")
    check(err)
    
    lines := strings.Split(string(dat), "\n")

    // construct lists
    left_list := []int{}
    right_list := []int{}

    for i := range len(lines) - 1 {
        numbers := strings.Split(lines[i], "   ")

        left_num, err := strconv.Atoi(numbers[0])
        check(err)
        right_num, err := strconv.Atoi(numbers[1])
        check(err)

        left_list = append(left_list, left_num)
        right_list = append(right_list, right_num)
    }
    
    // sort right_list
    sort.Ints(right_list)

    // count similarity
    score := 0
    for i := range left_list {
        score += left_list[i] * count_sorted(right_list, left_list[i])
    }

    fmt.Println(score)
}