TaskG

#include <iostream>
#include <string>
#include <set>

using namespace std;

int main()
{
    string str, res = "";
    set<char> s;
    cin >> str;
    for (int i = 0; i < str.size(); i++)
        if (s.find(str[i]) == s.end())
        {
            s.insert(str[i]);
            res += str[i];
        }
    cout << res << endl;
}