Find the digital sum

A number N is passed as an input to the program. The program must print the digital sum of the number. Note: The digital sum of a number is defined as the recursive sum of digits of a number till it reaches a single digit. 

Boundary Conditions: 0 < N < 10000000 

Input Format: First line will contain the number N. 

Output Format: First line will contain the digital sum of the number N. 

Sample Input/Output: Example 1: 

Input: 

45102 

Output: 

3 

Explanation: 4+5+1+0+2 = 12. But 12 is a two digit number. We need to recursively add till the sum is a single digit. So 1+2 = 3. 

Example 2: 

Input: 

22311 

Output:

9 

Explanation: 2+2+3+1+1 = 9 

Example 3: 

Input: 

9879871 

Output: 

4 

Explanation: 9+8+7+9+8+7+1 = 49. But 49 is a two digit number. We need to recursively add till the sum is a single digit. So 4+9 = 13. So again adding 1+3=4.

Source Code: //Python

n=int(input())

s=0

while n>0 or s>9:

    if n==0:

        n=s

        s=0

    s+=n%10

    n//=10

print(s)