using System;
using System.Collections.Generic;
using System.Linq;

internal class Program
{
    public static void Main(string[] args)
    {
        var n = int.Parse(Console.ReadLine());
        long sum = 0;
        for (int i = 0; i < n; i++)
        {
            var dateTimes = Console.ReadLine().Split(' ').Select(DateTime.Parse).ToArray();
            if (dateTimes[1].CompareTo(dateTimes[0]) < 0)
            {
                sum += (dateTimes[1].AddDays(1).ToBinary() - dateTimes[0].ToBinary());
            }
            else
            {
                sum += (dateTimes[1].ToBinary() - dateTimes[0].ToBinary());
            }
        }
        Console.WriteLine(TimeSpan.FromTicks(sum).TotalMinutes);
    }
}