#include <stdio.h>
int sum (int n)
{
    int x,sum=0;
    while(n>0)
    {
        x=n%10;
        sum=sum+x;
        n=n/10;
    }
        printf("%d",sum);
}

int main() {
    int n,sum=0,x;
    scanf("%d",&n);
    if(n<=0)
    {
        printf("invalid input");
        return 0;
    }
    sum(n);
        return 0;
    }