How to calculate sum of digits

CODE

How to calculate sum of digits

If a five digit number is input through the keyboard,write a program to calculate the sum of its digits

int main()

{

    int num,sum,r1,r2,r3,r4;

    printf("\n enter a 5 digit number:");

    scanf("\n %d",&num);                                                 

    r1=num%10;

    num=num/10;

    r2=num%10;

    num=num/10;

    r3=num%10;

    num=num/10;

    r4=num%10;

    num=num/10;

    sum=r1+r2+r3+r4+num;

    printf("\n sum of digits:%d",sum);

}

Output:

enter a 5 digit number:

12345

 sum of digits:15