#include <stdio.h>
struct Number{
    int num;
    int sum;
};
int calculateSum(struct Number*n){
    if(n->num <0)
    return -1;
    int temp = n->num
    n->sum = 0
    while(temp > 0){
        n->sum += temp % 10
        temp/= 10
    }
    return n->sum;
}
int main(){
    struct Number n;
    scanf("%d",&n.num);
    int result = calculate(&n);
    if(result == -1)
    printf("Invalid input");
    else
    printf("%d",n.sum);
    return 0;
}