#include<bits/stdc++.h>
using namespace std;

int main() {
	string n; cin >> n;
	if(n[0] != '1' or n == "1") {
		cout << "-1" << '\n';
		return 0;
	}
	int nn = n.size();
	for(int i = 1; i < nn; ++i) {
		if(n[i] != '3') {
			cout << "-1" << '\n';
			return 0;
		}
	}
	cout << nn - 1 << '\n';
	return 0;
}