#include <iostream>
#include <string>

using namespace std;

int main() {

	string C;
	cin >> C;
	
	int count = 0;
	for (unsigned int i = 0; i < C.length(); i++) {
		if (C[i] == '0') {
			count++;
		}
	}

	cout << C.length() - 1 - count << endl;

}