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

int main() {
	int N;
	cin >> N;

	int c = 0;
	while (N > 0) {
		if (N % 10 == 3) {
			c++;
			N /= 10;
			if (N == 1) break;
		}
		else {
			c = -1;
			break;
		}
	}

	cout << c << endl;
}