C Language - find sum of digits

Q13. WAP to find sum of digits.

#include<stdio.h>
#include<conio.h>
void main()
{
    int n, a, s=0;
    printf("Enter number: ");
    scanf("%d",&n);
    while(n<0)
    {
        a=n%10;
        s=s+a;
        n=n/10;
    }
    printf("Sum of digit is %d",s);
    getch();
}

Enter number: 155
Sum of digit is 11