#include <iostream>
#include <regex>
#include <algorithm>
using namespace std;

int main() {
    regex re("^1(0+)7$");
    string N;
    cin >> N;
    smatch sm;
    if (regex_match(N, sm, re)) {
        string sms = sm[0];
        int cnt = count(sms.begin(), sms.end(), '0');
        cout << max(cnt - 8, 8 - cnt) << endl;
    }
    return 0;
}