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

void main(void){
    char c[1000000] = "a";
    scanf("%s",c);
	int count = 0; 
    for(int i = 1;i < (int)strlen(c);i++){
		if(c[i] != '0'){
			count++;
		}
	}
	printf("%d",count);  
}