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;
  bool isprime(long long k) {
    for (long long i = 2; i <= sqrt(k); i++)
      if (k % i == 0) return false;
    return true;
  }
  long long bm(long long a, long long b, long long mod) {
    if (b == 0) return 1;
    long long t = bm(a, b / 2, mod);
    t = t * t % mod;
    return (b % 2 == 1 ? t * a % mod : t);
  }
  long long inv(long long a, long long mod) { return bm(a, mod - 2, mod); }
  void gay(long long TC) { cout << "Case #" << TC << ": "; }
  void solve(long long TC) {
    string s;
    cin >> s;
    long long n = s.length();
    if (n % 2) {
      cout << "NO\n";
      return;
    }
    if (s.substr(0, n / 2) != s.substr(n / 2, n / 2)) {
      cout << "NO\n";
    } else
      cout << "YES\n";
  }
  signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    long long t = 1;
    cin >> t;
    for (long long i = 1; i <= t; i++) solve(i);
    return 0;
  }
  