/* kertaus 4 */

#include <stdio.h>

struct complex {
  double re;
  double im;
};

struct complex cprod(struct complex a, struct complex b)
{
  struct complex p;
  p.re = a.re * b.re - a.im * b.im;
  p.im = a.re * b.im + a.im * b.re;
  return (p);
}

main()
{
  struct complex a = {0, 1}, b = {0, 1}, c;
  c = cprod(a, b);
  printf("c.re = %lf, c.im = %lf\n", c.re, c.im);
}