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 Main {
  
      public static void main(String[] args) {
          Scanner in = new Scanner(System.in);
          int t = in.nextInt();
          in.nextLine();
          StringBuilder sb = new StringBuilder();
          for(int T = 0; T < t; ++T) {
              String s = in.nextLine();
              int n = s.length();
              if(n % 2 == 0) {
                  String first = s.substring(0, n / 2);
                  String second = s.substring(n / 2, n);
                  if(first.equals(second)) {
                      sb.append("YES\n");
                  } else {
                      sb.append("NO\n");
                  }
              } else {
                  sb.append("NO\n");
              }
          }
          System.out.println(sb.toString());
      }
  }