//方法很多,翻转字符串,用集合工具翻转,或者数组倒叙都可以办到!
import java.util.Scanner;
public class Test {
public static void main(String[] args) {
//用char数组有点多余!String就可以!
char[] chs=new Scanner(System.in).nextLine().toCharArray();
for (int i = chs.length-1; i >0 ; i--)
if(i%2!=0)
System.out.print(chs[i]);
}
}