#include "bits/stdc++.h"

using namespace std;

void solve()
{
	string S;
	cin >> S;
	bool ok = S[0] == '1' && (int)S.size() > 1;
	for (int i = 1; i < (int)S.size(); i++)
	{
		ok &= S[i] == '3';
	}
	cout << (ok ? (int)S.size()-1 : -1) << endl;
}

int main(void)
{
	solve();
	//cout << "yui(*-v・)yui" << endl;
	return 0;
}