#include<stdio.h>
struct Number{
    int value;
};
int main()
{
    struct Number n;
    int sum=0;
    scanf("%d",&n;
    if(n,value<0)
    {
        printf("Invalid input");
        return0;
    }
    int temp=n.value;
    while (temp>0)
    {
        sum+=temp%10;
        temp/=10;
    }
    printf("%d\n",sum);
    return 0;
}