/* 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) throws java.lang.Exception
	{
 
		String s = "aaabbaa";
		Pattern pattern = Pattern.compile("(\\w)\\1{2,}|(\\w)\\2");
		Matcher matcher = pattern.matcher(s);
		while (matcher.find()){
			if (matcher.group(2) != null)
			    System.out.println(matcher.group(2)); 
		} 
	}
}

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