практикум 3.1

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            double a = double.Parse(Console.ReadLine());
            Console.WriteLine(f(a));
            Console.ReadLine();
        }
        static double f(double x)
        {
            return Math.Log10(x-1);
           }
        }
}