using System; using System.IO; using System.Linq; using System.Collections; using System.Collections.Generic; using System.Text; using System.Numerics; using System.Threading.Tasks; using System.Text.RegularExpressions; using static System.Math; using Debug = System.Diagnostics.Debug; using MethodImplOptions = System.Runtime.CompilerServices.MethodImplOptions; using MethodImplAttribute = System.Runtime.CompilerServices.MethodImplAttribute; static class P { static void Main() { int n = int.Parse(Console.ReadLine()); Console.WriteLine(n >= 15 ? n - 7 : -1); } }