using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static long NN => long.Parse(ReadLine());
    static long[] NList => ReadLine().Split().Select(long.Parse).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        var (h, m) = (c[0], c[1]);
        var dh = (60 * h + m) * 60 % 43200;
        var dm = 43200 / 60 * m;
        var time = 0;
        while (true)
        {
            var ndh = dh + 1;
            var ndm = dm + 12;
            if (dh == dm || (dh > dm && ndh < ndm))
            {
                WriteLine(time);
                return;
            }
            ++time;
            dh = ndh % 43200;
            dm = ndm % 43200;
        }
    }
}