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

int main()
{
	string rez="";
	string str;
	int i, currentPos;
	while(cin>>str)
	{
		int p=str.size();
		currentPos=0;
		for(i=0; i<p; i++)
		{
			if(rez.find(str[i], currentPos)==rez.npos)
			{
				string d="";
				d+=str[i];
				rez.insert(currentPos, d);
				currentPos+=1;
			}
			else
			{
				currentPos=rez.find(str[i], currentPos)+1;
			}
		}
		cout<<rez;
	}
	cout<<rez;
	
}