#include <iostream>
#include <set>
using namespace std;

int main() {
    int N;
    cin >> N;
    
    set<int> nums;
    for(int i = 0; i < N; i++) {
        int num;
        cin >> num;
        nums.insert(num);
    }
    
    cout << nums.size() << endl;
    for(auto it = nums.begin(); it != nums.end(); it++) {
        if(it != nums.begin()) cout << " ";
        cout << *it;
    }
    return 0;
}

#include using namespace std;

int a[10005]; int box[10005]; int main() { int n; cin >> n; for(int i = 1;i <= n;i++) { int score; cin >> score; box[score]++; } int cur = 0; for(int i = 1;i <= 10000;i++) { if(box[i] > 0) { cur++; a[cur] = i; } } cout << cur << endl; for(int i = 1;i <= cur;i++) { cout<< a[i] << " "; } return 0; }

include <bits/stdc++.h>

using namespace std; int a[100001],n;; int main(){ cin>>n; for(int i = 1;i<= n;i++) cin>>a[i]; for(int i = 1;i<=n;i++) if(a[i]!=0) for(int j = i+1;j<=n;j++) if(a[j]==a[i]) a[j]=0;

for(int i = 1;i<=n;i++){
	int k=i;
	for(int j = i+1;j<=n;j++)
	    if(a[j]<a[k])
	        k=j;
	swap(a[i],a[k]);
}
int ans=0;
for(int i = 1;i<=n;i++)
	if(a[i]!=0)
	   ans++;
cout<<ans<<endl;
for(int i = 1;i<=n;i++)
    if(a[i]!=0)
        cout<<a[i]<<" ";
return 0;

}

#include<iostream>
using namespace std;
int n,a[10001],b[1001],cnt;
int main(){
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>a[i];
		if(b[a[i]]==0){
			b[a[i]]=1;
			cnt++;
		}
	}
	cout<<cnt<<endl;
	for(int i=1;i<=1000;i++){
		if(b[i])cout<<i<<" ";
	}
}

#include<bits/stdc++.h>
using namespace std;
int n,a[110],b[1010],c[110],x;
int main(){
	
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>a[i];
		b[a[i]]++;
	}
	for(int i=1;i<=1000;i++){
		if(b[i]){
			
		    c[x]=i;
		    x++;
	    }
	}
	sort(c,c+x);
	cout<<x<<endl;
	for(int i=0;i<x;i++){
		cout<<c[i]<<' ';
	}
	return 0;
}