题解

#include<bits/stdc++.h>
using namespace std;
int main(){
    set<int>val;
    int n;
    cin>>n;
    for(int i=1;i<=n;i++){
        int s;
        cin>>s;
        val.insert(s);
    }
    cout<<val.size()<<endl;
    for(auto it:val){
        cout<<it<<" ";
    }
    return 0;
}