Programming in C to reverse a number

#include<stdio.h>
#include<conio.h>
void main()
{
int a,r=0,s;
clrscr();
printf("\nEnter the number which is to be reversed (upto 4 numbers only):");
scanf("%d",&a);
while(a>0)
{
s=a%10;
a=a-s;
r=(r*10)+s;
a=a/10;
}
printf("\n Reversed number: %d",r);
getch();
}