import java.util.Scanner;

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