import java.io.*;

public class AsciiDiag{
   public static void main(String[] args){
      try{
         int i = 0;
         String s = "";
         BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
         String line = in.readLine();
         while(line != null){
            s += line.charAt(i);
            i++;
            line = in.readLine();   
         }
         System.out.println(s);
}catch(Exception e){e.printStackTrace();}
   }
}