using System; using System.IO; using System.Linq; using System.Collections; using System.Collections.Generic; using System.Numerics; using System.Diagnostics; using System.Text; using System.Text.RegularExpressions; using System.Threading.Tasks; using static System.Math; using MethodImplOptions = System.Runtime.CompilerServices.MethodImplOptions; using MethodImplAttribute = System.Runtime.CompilerServices.MethodImplAttribute; static class P { static void Main() { var abc = Console.ReadLine().Split().Select(double.Parse).ToList(); Console.WriteLine(abc[0] * 60 - abc[1] <= 0 ? "-1" : ((long)Ceiling(abc[2] / (abc[0] * 60 - abc[1]) * 3600)).ToString()); } }