package main

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

func main() {
  left := map[int]int{};
  right := map[int]int{};
  reader := bufio.NewReader(os.Stdin)

  for {
    raw, _, _ := reader.ReadLine()
    line := string(raw)

    if strings.Trim(line, " ") == "" {
      break
    }

    values := strings.Split(line, "   ")

    l, _ := strconv.Atoi(values[0])
    r, _ := strconv.Atoi(values[1])

    left[l] = left[l] + 1
    right[r] = right[r] + 1
  }

  ans := part2(left, right)

  fmt.Println("", ans)
}

func part2(left map[int]int, right map[int]int) int {
  sum := 0

  for key, l_count := range left {
    count := right[key]
    sum += l_count * count * key
  }

  return sum;
}