class S{public static void main(String[]a){int c=-1,f=-1;try{do{c=System.in.read();f=System.in.read();if(f>=0)System.out.write(f);if(c>=0)System.out.write(c);}while(c>=0||f>=0);}catch(java.io.IOException e){System.err.println(e);}System.out.flush();}}