import java.util.*;
import java.lang.*;
import java.io.*;

class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		List<String> strs = Arrays.asList("ab","aabb","aaaabbbb","aab","aaaabb");
		for (String str : strs)
			System.out.println(str + ": " + str.matches("(?:aa(?=(?:aa)*(\\1?+b)))+\\1"));

	}
}