Problem
Add up every decimal digit of n. For 352 the digits are 3, 5 and 2.
Implement sum_of_digits(n).
Input
n: A positive integer.
Output
Return the sum of its digits.
Constraints
1 ≤ n ≤ 10¹⁸
Examples
Example 1
Input:
n = 352
Expected output:
expected = 10Input:
long long n = 352;
Expected output:
long long expected = 10;Input:
long n = 352;
Expected output:
long expected = 10;Explanation
3 + 5 + 2 = 10.
Example 2
Input:
n = 1000
Expected output:
expected = 1Input:
long long n = 1000;
Expected output:
long long expected = 1;Input:
long n = 1000;
Expected output:
long expected = 1;Explanation
1 + 0 + 0 + 0 = 1.