using System;
namespace _1
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine(AddF("11"));
Console.WriteLine(AddF("1T1"));
Console.WriteLine(AddF("X"));
}
static string AddF(string s)
{
if (s.Length < 4)
s = s.PadLeft(4, 'F');
return s;
}
}
}
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