C :

#include <stdio.h>
void main()
{
	int x;
	scanf("%d",&x);
	printf("%d\n",x/10%10+x%10+x/100);
}

C++ :

#include<iostream>
using namespace std;
int main()
{
    int x;
    cin>>x;
    cout<<x/100+x/10%10+x%10<<endl;
    //cin.get();cin.get();
    return 0;
}

Python :

# coding=utf-8
n=int(input())
sum=0
while n>0:
    sum+=n%10
    n=n//10
print(sum)