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;
  const int64_t mod = 1e9 + 7, INF = 1e18L + 5, N = 2e5 + 5;
  const string yes = "YES", no = "NO";
  void pavvo() {
    string s;
    cin >> s;
    int64_t n = s.size();
    string t = s.substr(0, n / 2);
    string p = s.substr(n / 2, n);
    ;
    cout << ((t == p) ? yes : no) << '\n';
  }
  signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int64_t T = 1;
    cin >> T;
    for (int64_t test = 1; test <= T; ++test) {
      pavvo();
    }
    cerr << "Time : " << 1000 * ((double)clock()) / (double)CLOCKS_PER_SEC
         << "ms\n";
    return 0;
  }
  