#include <stdio.h>

void swap(int *a, int *b) {
  int tmp = *a;
  *a = *b;
  *b = tmp;
}

int main(int argc, char **argv) {
  int a = 42, b = -7;

  swap(&a, &b);
  printf("a: %d, b: %d\n", a, b);
  return 0;
}