using System;
using System.Linq;
using System.Collections.Generic;

public class Test
{
	public static void Main()
	{
        string str = "12.34.56.78";
        Char replaceChar = '.';
        int lastIndex = str.LastIndexOf(replaceChar);
        if (lastIndex != -1)
        {
            IEnumerable<Char> chars = str
                .Where((c, i) => c != replaceChar || i == lastIndex);
            str = new string(chars.ToArray());
        }
        Console.Write(str);
	}
}