I need help

Question

#include <stdio.h>

long reverse(long);

int main()
{
long n, r;

scanf("%ld", &n);

r = reverse(n);

printf("%ld\n", r);

return 0;
}

long reverse(long n) {
static long r = 0;

if (n == 0)
return 0;

r = r * 10;
r = r + n % 10;
reverse(n/10);
return r;
}
It is a program for reversing a number
I can't understand part after scanf("%ld"&n)
Please explain me part after that briefly

Answer 1

I think it's wrong but I'm not sure