#include <iostream>
using namespace std;

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

    int i=0;

    while(n != 0) {
        if(n%10 == 3){
            i++;
            n /= 10;
        }
        else if(n==1 && i != 0) {
            break;
        }
        else {
            cout << -1 << endl;
            return 0;
        }
    }

    cout << i << endl;
}