#include <stdio.h>
#include <stdlib.h>

int course1 = 15213;
int course2 = 18213;

void swap(int* p, int* q);

void call_swap() {
  swap(&course1, &course2);
}

int main() {
  printf("Initially: course1 = %d, course2 = %d\n", course1, course2);
  call_swap();
  printf("Finally: course1 = %d, course2 = %d\n", course1, course2);
  return 0;
}