#include "bits/stdc++.h"

using namespace std;

using ll = long long;
using ld = long double;

const double PI = 3.1415926535897932384626433832795;

const int dx[] = { 0, 1, 0, -1 };
const int dy[] = { -1, 0, 1, 0 };

int gcd(int x, int y) { return y ? gcd(y, x % y) : abs(x); }
ll gcd(ll x, ll y) { return y ? gcd(y, x % y) : abs(x); }
int lcm(int x, int y) { return x / gcd(x, y) * y; }
ll lcm(ll x, ll y) { return x / gcd(x, y) * y; }

int solve(string s) {
	if (s.size() == 1 || s[0] != '1') {
		return -1;
	}

	bool is3only = true;
	for (int i = 1; i < s.size(); i++) {
		if (s[i] != '3') {
			is3only = false;
			break;
		}
	}

	return is3only ? s.size() - 1 : -1;
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);

	string s;
	cin >> s;

	cout << solve(s) << endl;
	return 0;
}