Envío 2095

Código

import java.util.Scanner;

class Main{

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String s = sc.nextLine();
		sc.close();
		int n = s.length();
		int arr[] = new int[n];
		int pos = 0;
		for (int i = 1; i < n; i++) {
			while (s.charAt(i) != s.charAt(pos) && pos > 0) {
				pos = arr[pos - 1];
			}
			if (s.charAt(i) == s.charAt(pos)) {
				pos++;
			}
			arr[i] = pos;
		}
		System.out.println(arr[n - 1]);

	}
}