#include <stdio.h>

int main(void) {

    char s[101];
	int i = 0;
	int count = 0;
	scanf("%s", s);
	while(s[i] != 0){
		if(s[i] != '0'){
			count++;
		}
		i++;
	}
	printf("%d\n", count - 1);

	return 0;
}