public void Main(string[] args)
string str = "СОУ Паисий Хилендарски ";
string str2 = str.Remove(0,3);
string str3 = str.Insert(4,"е наречено ");
string str4 = "Linux, Windows It is not Linux, it is GNU/Linux. Linux is merely the kernel, while GNU adds the functionality...";
string str5 = str4.Replace("Linux","*****");
string alpha = "ШОКОЛАД";
string lowerAlpha = alpha.ToLower();
Console.WriteLine(lowerAlpha);
string alpha2 = "иван иванов петров";
string upperAlpha = alpha2.ToUpper();
Console.WriteLine(upperAlpha);