#include<iostream>
#include<string>
#include<math.h>
#include<stdlib.h>
#include<string>
#include<cstdio>
#include<stack>
using namespace std;
int main() {
	int n;
	cin >> n;
	int sum = 0;
	int f = 0;
	for (int i = 1; i <= n ; i = i * 10) {
		sum = sum + (n / i) % 10;
		if ((n / i) % 10 != 3) {
			if (i * 10 > n) {
				if ((n / i) % 10 == 1) {
					cout << (sum - 1) / 3;
					break;
				}
			}
			cout << -1;
			break;
		}
	}
}