/*
What does this program print if the user types Hello World?
*/

#include <stdio.h>
#include <ctype.h>

int main(void)
{
  int c;

  while ((c = getchar()) != EOF) {
    putchar(c);
    putchar(islower(c) ? toupper(c) : tolower(c));
  }
  return 0;
}