#include <algorithm>
#include <iostream>
#include <string>

int main()
{
  std::string s = "Hallo, Welt";
  std::cout << s << '\n';
  std::sort(begin(s), end(s));

  auto neues_ende = std::unique(begin(s), end(s));
  s.erase(neues_ende, s(end));

  std::cout << s << '\n';
}