#include<iostream>
#include<stdio.h>
using namespace std;
int main()
{char c[200000],d;
int i=0,j,k;
while(cin>>c[i]&&i<200000)
{char d=c[i];
if(i!=0&&c[i-1]==d){c[i]=c[i-1]=NULL;i=i-1;}
else if(int(d)==32){c[i]=NULL;}
else i++;
}

cout<<c<<endl;
return 0;
}


Edited by author 20.07.2012 19:31