#include <stdio.h>
#include <string.h>

void main(void){
	char c[10000000] = "a";
	scanf("%s",&c);
	int count = 0;
	for(int i = 1;i < (int)strlen(c)-1;i++){
		if(c[i] != '0'){
			count++;
		}
	}
	printf("%d",count);
}