using System;

public class Program

{

    public static void Main()

    {

        var a = new Affine();

        Console.WriteLine(a.Encrypt("affi"));

        Console.WriteLine(a.Decrypt("*MMb"));

    }

}

​

public class Affine

{

    int die = 128;

    int k1 = 7;

    int k2 = 3;

    int ki = 55;

    public char CharEncryptor(char c)

    {return (char)((k1*(int)c+k2)%die);}

    public string Encrypt(string s)

    {

        string res = "";

        string pizda = ",./!'\"[](){}!@#$%^&*() ";

        foreach (char i in s)

        {

            if (!pizda.Contains(i.ToString())) {res += CharEncryptor(i);}

            else{res += i;}

        }

        return res;

    }

    public char CharDecryptor(char c)

    {return (char)((ki * ((int)c -k2))%die);}

    public string Decrypt(string s)

    {

        string res = "";

        string pizda = " ";

        foreach (char i in s)

        {

            if (!pizda.Contains(i.ToString())) {res += CharDecryptor(i);}

            else{res += i;}

        }

        return res;

    }

}