#include <iostream>
#include <string>
using namespace std;

int main()
{
	int result;
	string s;

	cin >> s;

	if (s[s.size() - 1] % 2) result = 1;
	else result = 0;

	while (s!="1") {
		string s2;
		s2 = s;
		for (int i = 0; i < (int)s.size(); i++) {
			int x;
			if (i!=0&&((int)s[i - 1] - (int)'0') % 2) {
				if (((int)s[i] - (int)'0') % 2) {
					x = ((int)s[i] - (int)'0')-1 + (5 - (((int)s[i] - (int)'0')-1)/2);
				}
				else {
					x = ((int)s[i] - (int)'0') + (5 - ((int)s[i] - (int)'0') / 2);
				}
			}
			else {
				x = ((int)s[i] - (int)'0') / 2;					
			}

			s2[i] = to_string(x)[0];
		}
		s = s2;
		if (s[0] == '0') {
			s.erase(s.begin());
		}
		if (s[s.size() - 1]%2) result++;
	}

	cout << result << endl;

    return 0;
}