C Program for sum of digits using function

Program

//program for sum of digits using function
#include<stdio.h>
int sum(int);
void main()
{
int no,ans;
printf("Enter the no.");
scanf("%d",&no);
ans=sum(no);
printf("sum of digits=%d\n",ans);
}
int sum(int n)
{
int d,sum=0;
while(n>0)
{
d=n%10;
n=n/10;
sum=sum+d;
}
return(sum);
}

Output
Enter the no.561
sum of digits=12