[编程题] 偶串分析代码

import java.util.*;


public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        
        String s = in.nextLine();
        
        in.close();
        
        System.out.println(helper(s));
    }
    
    
    private static int helper(String s) {
        
        for(int i=s.length()-1;i>0;i--) {
            if(isString(s.substring(0, i)))
                return i;
        }
        
        return 1;
    }
    
    private static boolean isString(String s) {
        String front = s.substring(0, s.length()/2);
        
        String end = s.substring(s.length()/2, s.length());
        
        return front.equals(end);
    }
}