3.find sum of first and last digit of a number

#include<stdio.h>
int main()
{
int num,sum=0,first,last;
printf("enter any number:");
scanf("%d",&num);
last=num % 10;
first=num;
while(num>=10)
{
num=num/10;
}
first=num;
sum=first+last;
printf("%d",sum);

return 0;

}