#include <iostream>
using namespace std;
int main(void){
    // Your code here!
    char s[100];
    int a, i;
    scanf("%s", s);
    for(i = 0; s[i]!=NULL; s[i]==NULL){
        a += s[i] - '0';
        i++;
    }
    
    printf("%d", a);
    //while(s[]){
    //printf("%d\n", a - 'i');
    //i++;
    
    //}

    return 0;
}