C :

#include <stdio.h>
int main() {
    int a,s;
    while (scanf("%d", &a) != EOF) {
        s = 0;
        while (a!=0) {
          s += a%10;
          a=a/10;
        }
        printf("%d\n",s);
    }
	return 0;
}

C++ :

#include<bits/stdc++.h>
using namespace std;
unsigned long long a,s;
int main()
{
	while(cin>>a)
	{
		while(a!=0)
		{
			s+=a%10;
			a/=10;
		}
		cout<<s<<endl;
		s=0;
	}
   return 0;
}