package main

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

var sc = bufio.NewScanner(os.Stdin)

// var rdr = bufio.NewReaderSize(os.Stdin, 1000000)

func nextLine() string {
	sc.Scan()
	return sc.Text()
}

func nextInt() int {
	i, _ := strconv.Atoi(nextLine())
	return i
}

func nextFloat() float64 {
	f, _ := strconv.ParseFloat(nextLine(), 64)
	return f
}

// func readLine() string {
// buf := make([]byte, 0, 1000000)
// for {
// l, p, e := rdr.ReadLine()
// if e != nil {
// panic(e)
// }
// buf = append(buf, l...)
// if !p {
// break
// }
// }
// return string(buf)
// }

func main() {
	sc.Split(bufio.ScanWords)
	var total int

	n := nextInt()

	for i := 0; i < n; i++ {
		a, b := strings.Split(nextLine(), ":"), strings.Split(nextLine(), ":")
		ah, _ := strconv.Atoi(a[0])
		am, _ := strconv.Atoi(a[1])
		bh, _ := strconv.Atoi(b[0])
		bm, _ := strconv.Atoi(b[1])
		at := time.Date(1, time.November, 1, ah, am, 0, 0, time.UTC)
		day := 1
		if ah > bh {
			day = 2
		}
		bt := time.Date(1, time.November, day, bh, bm, 0, 0, time.UTC)
		d := bt.Sub(at)
		total += int(d.Minutes())
	}
	fmt.Println(total)
}