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: #include <bits/stdc++.h>
  using namespace std;
  long long sigma(long long l, long long r) {
    return ((r * (r + 1)) / 2) - ((l * (l - 1)) / 2);
  }
  long long gcd(long long a, long long b) { return b ? gcd(b, a % b) : a; }
  long long lcm(long long a, long long b) { return a / gcd(a, b) * b; }
  long long dx[8] = {0, 0, 1, -1, 1, -1, 1, -1};
  long long dy[8] = {1, -1, 0, 0, 1, -1, -1, 1};
  int32_t main() {
    ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    long long t;
    cin >> t;
    while (t--) {
      string x;
      cin >> x;
      long long n = x.size() / 2;
      if (x.size() % 2)
        cout << "NO" << '\n';
      else {
        string s = x.substr(0, n);
        string d = x.substr(n, n);
        cout << (s == d ? "YES" : "NO") << '\n';
      }
    }
    return 0;
  }
  