#include <bits/stdc++.h>

using namespace std;
#define ll long long

int main(){
    ll numbers, maxSize;
    cin >> numbers >> maxSize;
    set<string> s;
    queue<string> q;
    ll setSize=0;
    for(ll i=0; i<numbers; i++){
        string message;
        cin>>message;
        if(i==0){
            q.push(message);
            s.insert(message);
            setSize=s.size();
        }
        else{
            if(q.size()==maxSize && message!= q.front()){
                setSize=s.size();
                s.insert(message);
                if(setSize<s.size()){
                    q.pop();
                    q.push(message);
                }
            }
            else{
                if(q.size()<maxSize){
                    setSize=s.size();
                    s.insert(message);
                    if(setSize<s.size()){
                        q.push(message);
                    }
                }
            }
        }
    }
    cout<<q.size()<<endl;
    vector<string> myv;
    while(!q.empty()){
            myv.push_back(q.front());
            q.pop();
        }
    for(ll i=myv.size()-1; i>-1; i--){
        cout<<myv[i]<<" ";
    }
    cout<<endl;    
           
       
}