package algo; import java.util.Scanner; public class sample7 { public static void main(String[] args) { Scanner sc = new Scanner(System.in); String S = sc.next(); if(S.length() % 2 == 1) { System.out.println("NO"); } else { String ss = S.substring(S.length() / 2); String sss = S.substring(0, S.length() / 2); if(sss.equals(ss)) { System.out.println("YES"); } else { System.out.println("NO"); } } } }