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.*;
  public class r
  {
           public static void main(String args[])
           {
                    Scanner ob=new Scanner (System.in);
                    int t=ob.nextInt();
                    
                    while(t-->0)
                    {
                             String s=ob.next();
                             int l=s.length();
                             String str="";
                             
                             if(l%2==0)
                             {
                                 if((s.substring(0,(l/2))).equals(s.substring((l/2),l)))
                                 str="YES";
                                 else
                                 str="NO";
                             }
                             else
                             str="NO";
                              
                             System.out.println(str);
                             
                    }
                    
                    
                    
                    
                    
                    
                    
                    
                    
           }
  }