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

int main() {
	string S;
	bool check = true;
	cin >> S;
	if (S == "1") { cout << -1 << endl; return 0; }
	if (S[0] != '1') check = false;
	for (int i = 1; i < S.size(); i++) {
		if (S[i] != '3') check = false;
	}
	if (check) cout << S.size() - 1 << endl;
	else cout << -1 << endl;
}