func_code_string: #include <bits/stdc++.h>   using namespace std;   void solve() {     int N, K;     cin >> N >> K;     set<int> s;     for (int i = 0; i < N; i++) {       int a;       cin >> a;       s.insert(a);     }     if (s.size() > K) {       cout << -1 << endl;       return;     }     cout << N * K << endl;     for (int i = 0; i < N; i++) {       for (int b : s) cout << b <<    ;       for (int j = 0; j < K - (int)s.size(); j++) cout << 1 <<    ;     }     cout << endl;   }   int main() {     int t;     cin >> t;     while (t--) solve();   }   