#include <bits/stdc++.h>   using namespace std;   int main(int argc, char *argv[]) {     long long n, k, a[55];     cin >> n >> k;     for (int i = 1; i <= n; i++) cin >> a[i];     sort(a + 1, a + 1 + n);     if (k > n)       cout << -1 << endl;     else {       cout << a[n + 1 - k] <<     << a[n + 1 - k] << endl;     }     return EXIT_SUCCESS;   }   