#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#define int long long
using namespace std;
signed main() {
	string s; cin >> s;
	bool b = 1;
	if (s[0] != '1')b = 0;
	for (int i = 1; i < s.size(); i++)if (s[i] != '3')b = 0;
	cout << (b ? s.size() - 1 : -1) << endl;
}