#include <bits/stdc++.h>
using namespace std;
#define int long long
#define double long double
#define DEBUG 1
#ifdef DEBUG
#define OUT(x) cerr << (#x) << '=' << (x) << endl
#define OUT2(c) cerr << (#c) << " = {"; for (auto it = (c).begin(); it != (c).end(); ++it) cerr << (it == (c).begin() ? "" : ", ") << *it; cerr << "}" << endl;
#else
#define OUT(x)
#define OUT2(c)
#endif
void solve() {
int n, k; cin >> n >> k;
vector<int> v(n);
for(int i = 0; i < n; i++){
cin >> v[i];
}
for(int l = 0; l < n; l++){
for(int r = l; r < n; r++){
int len = r - l + 1;
if(len % k != 0) continue;
int sz = len / k;
bool passes = 1;
for(int i = l + sz; i <= r; i++){
if(v[i] != v[i - sz]) passes = 0;
}
if(passes){
cout << sz << '\n';
for(int i = l; i < l + sz; i++){
cout << v[i] << " ";
}
return;
}
}
}
cout << "-1\n";
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
int tt; tt = 1;
while (tt--) {
solve();
}
}
