import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        char[] arr = sc.next().toCharArray();
        if (arr[0] != '1') {
            System.out.println(-1);
            return;
        }
        for (int i = 1; i < arr.length; i++) {
            if (arr[i] != '3') {
                System.out.println(-1);
                return;
            }
        }
        System.out.println(arr.length - 1);
    }
}