using System;
public class Program
{
public static void Main()
string p1 = "12";
string p2 = null;
string p3 = null;
string p4 = "32";
string p1a = "12";
string p2a = null;
string p3a = "32";
string p4a = null;
Console.WriteLine(string.Concat(p1a, p2a, p3a, p4a));
}