zadatak1

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

int main(){
  char c;

  while((c=getchar())!=EOF)
  {
    if(isupper(c))  //A
      c=tolower(c); //a

    else if(islower(c))
      c=toupper(c);

    printf("%c\n",c );
  }
  return 0;
}