Reverse of a Number using Recursion In C and C++

#include<stdio.h>
int rev(int);
int s=0,r;
main()
{
int num,i,n;
scanf("%d",&num);
i=rev(num);
printf("%d",s);

}
int rev(int p)
{

if(p!=0)
{
r=p%10;
s=s*10+r;
rev(p/10);
}

return s;
}