description: A string is called square if it is some string written twice in a row. For example, the strings "aa", "abcabc", "abab" and "baabaa" are square. But the strings "aaa", "abaaab" and "abcdabc" are not square.
  
  For a given string s determine if it is square.
  
  Input
  
  The first line of input data contains an integer t (1 ≤ t ≤ 100) —the number of test cases.
  
  This is followed by t lines, each containing a description of one test case. The given strings consist only of lowercase Latin letters and have lengths between 1 and 100 inclusive.
  
  Output
  
  For each test case, output on a separate line:
  
    * YES if the string in the corresponding test case is square, 
    * NO otherwise. 
  
  
  
  You can output YES and NO in any case (for example, strings yEs, yes, Yes and YES will be recognized as a positive response).
  
  Example
  
  Input
  
  
  10
  a
  aa
  aaa
  aaaa
  abab
  abcabc
  abacaba
  xxyy
  xyyx
  xyxy
  
  
  Output
  
  
  NO
  YES
  NO
  YES
  YES
  YES
  NO
  NO
  NO
  YES
solution: 
  import java.util.*;
  import java.lang.*;
  import java.io.*;
  
  
  public class Main
  {
      static PrintWriter out = new PrintWriter(new BufferedOutputStream(System.out));
  	public static void main (String[] args) throws java.lang.Exception
  	{
  		FastReader sc = new FastReader();
  		
  		int t = sc.nextInt();
  		while(t-->0){
  		    String str = sc.nextLine();
  		    int len = str.length();
  		    
  		    if(len%2!=0){
  		        out.println("NO\n");out.flush();continue;
  		    }
  		    String s2 = str.substring(len/2);
  		    String s3 = str.substring(0, len/2);
  		    if(s2.equals(s3)){
  		        out.println("YES\n");
  		    }else{
  		        out.println("NO\n");
  		    }
  		    out.flush();
  		}
  		
  	}
  	
  	static class FastReader {
  			 BufferedReader br;
  			 StringTokenizer st;
  		 
  			 public FastReader()
  			 {
  				 br = new BufferedReader(new InputStreamReader(System.in));
  			 }
  		        
  			 String next()
  			 {
  				 while (st == null || !st.hasMoreElements()) {
  					 try {
  						 st = new StringTokenizer(br.readLine());
  					 }
  					 catch (IOException e) {
  						 e.printStackTrace();
  					 }
  				 }
  				 return st.nextToken();
  			 }
  		 
  			 int nextInt() { return Integer.parseInt(next()); }
  			 
  			 long nextLong() { return Long.parseLong(next()); }
  			 
  			 double nextDouble()
  			 {
  				 return Double.parseDouble(next());
  			 }	
  		 
  			 String nextLine()
  			 {
  				 String str = "";
  				 try {
  					 str = br.readLine();
  				 }
  				 catch (IOException e) {
  					 e.printStackTrace();
  				 }
  				 return str;
  			 }
  		 }	
  }
  