/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
import java.util.regex.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
    public static void main(String[] args) {
        String REC_PATTERN = "^(?>\\w+\\.){3}(.*)$";
        Pattern pattern = Pattern.compile(REC_PATTERN);
        Matcher m = pattern.matcher("ab.bc.de.ef");
        if (m.find())
            System.out.println(m.group(1));//output ef
        m = pattern.matcher("ab.bc.cd.de.11111");
        if (m.find())
            System.out.println(m.group(1));//output de.11111
    }
}

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