#include<bits/stdc++.h>
#define rep(i, x) for(ll i = 0; i < x; i++)
#define rep2(i, x) for(ll i = 1; i <= x; i++)
#define all(a) (a).begin(),(a).end()
using ll = long long;
using ld = long double;
using namespace std;
signed main() {
    string s; cin >> s;
    if (s == "1") { cout << "-1\n"; return 0; }
	rep(i, s.size()) {
		if (i == 0 && s[i] != '1') { cout << "-1\n"; return 0; }
		if (i != 0 && s[i] != '3') { cout << "-1\n"; return 0; }
	}
	cout << s.size() - 1 << endl;
	return 0;
}