Sum of digits

 

#include <bits/stdc++.h>
using namespace  std ;

int sum(int n){
    //Base case
    if (n==0) return 0;
    //Recursive case
    int smallAns = sum(n/10);
    //Calculation
    int last_digit = n%10 ;
    return  smallAns + last_digit ;

}

int main (){
    int n  ;
    cin >> n ;
    cout << sum(n) << '\n';

    return 0;
}