C program to add digits of a number

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#include<stdio.h>

int main(){

  int num,sum=0,r;

  printf("Enter a number: ");

  scanf("%d",&num);

  while(num){

      r=num%10;

      num=num/10;

      sum=sum+r;

  }

  printf("Sum of digits of number:  %d",sum);

  return 0;

}

Sample output:

Enter a number: 123

Sum of digits of number:  6

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