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

using namespace std;

string removeDup(string s)
{
   if (s.length() == 0)
   {
       return "";
   }

   size_t index = 0;
   string::iterator end = s.end();

   while (index < s.size()) {
       end = remove(s.begin()+index+1, end, s[index]);
       ++index;
   } 

   s.erase(end, s.end());
   return s;
}

int main()
{
   cout << removeDup("allcbbcd") << endl;

   return 0;
}