#include<bits/stdc++.h>
#define fi first
#define se second
#define pitem item*
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<ll> vl;
const int N=1e6+10;
const int SS=1<<19;
const int INFi=2e9;
const ll INFl=1e13;
const ll mod2=998244353;
const ll mod=1e9+7;
const ll mod3=1000696969;
const ll p=70032301;
const ull p2=913;
const int L=20;
int t[N];
void solve(){
int n,k;
cin>>n>>k;
for(int i=1;i<=n;i++) cin>>t[i];
for(int i=1;i<=n;i++){
for(int i2=i;i2<=n;i2++){
if((i2-i+1)%k) continue;
int dl=(i2-i+1)/k;
bool ok=1;
for(int xd=i+dl;xd<=i2;xd++)
if(t[xd]!=t[xd-dl]) ok=0;
if(ok){
cout<<dl<<"\n";
for(int xd=i;xd<i+dl;xd++) cout<<t[xd]<<" ";
cout<<"\n";
return;
}
}
}
cout<<-1<<"\n";
}
int main(){
ios_base::sync_with_stdio(0),cin.tie(0);
int tt=1;
while(tt--) solve();
}
