import java.util.Scanner;

public class Main {
	static public void main(String[]args) throws Exception {
		Scanner sc = new Scanner(System.in);
		String n = sc.next();
		printAns(n);
	}

	static void printAns(String s) throws Exception {
		if( isValid(s) ) {
			int ans = s.length() -1;
			System.out.println(ans);
		} else {
			System.out.println(-1);
		}
	}

	static boolean isValid(String s) throws Exception {

		if(s.charAt(0) != '1') return false;

		if(!s.contains("3")) return false;

		for(int i=1; i<s.length(); i++) {
			char c = s.charAt(i);
			if( c != '3') return false;
		}

		return true;
	}
}