#include <stdio.h>

void swap(int p, int q){
  int   tmp;

  tmp = p;
  p = q;
  q = tmp;
}


int main(void){
  int   a = 3, b = 7;

  printf("%d  %d\n", a, b);     /* 3  7 is printed */
  swap(a, b);
  printf("%d  %d\n", a, b);     /* 3  7 is printed */
  return 0;
}