set

#include <fstream>
#include <iostream>
#include <set>

using namespace std;

set <int> s;

int main()
{
    int i, x, n;
    set<int>::iterator it;
    ifstream fin("sir.in");
    fin >> n;
    for (i = 1; i <= n; i++)
    {
        fin >> x;
        s.insert(x);
    }
    fin.close();
    cout << s.size()<<"\n";

    if (s.find(3) != s.end())
        cout << "3 exista\n";
    else cout << "3 nu exista\n";

    for (it = s.begin(); it != s.end(); it++)
        cout << *it << " ";
    cout <<"\n";

    it = s.begin();
    advance(it, 4);
    s.erase(it);

    //s.erase(4);

    for (it = s.begin(); it != s.end(); it++)
        cout << *it << " ";
    cout <<"\n";

    return 0;
}