#include <avr/io.h>

#define READ_BIT(destiny, bit)            (((destiny) >> (bit)) & 1)
#define SET_BIT(destiny, bit)             (destiny) = (destiny) | (1 << (bit))
#define CLEAR_BIT(destiny, bit)           (destiny) = (destiny) & ~(1 << (bit))
#define WRITE_BIT(destiny, bit, value)    (destiny) = (value) ? SET_BIT((destiny), (bit)) : CLEAR_BIT((destiny), (bit))
#define TOGGLE_BIT(destiny, bit)          (destiny) = READ_BIT((destiny), (bit)) ? CLEAR_BIT((destiny), (bit)) : SET_BIT((destiny), (bit))

int main(void){
  SET_BIT(DDRC, DDC5);  // Setting pin A5 as output
  SET_BIT(DDRB, DDB5);  // Setting pin 13 as output
  CLEAR_BIT(DDRD, DDC3);  // Setting pin 3 as input
  SET_BIT(PORTD, PORTD3); // Enabling pin 3 pull-up resistor
  for(;;){
    WRITE_BIT(PORTC, PORTC5, READ_BIT(PIND, PIND3));  // Writing the state of pin 3 to pin A5
    WRITE_BIT(PORTB, PORTB5, !READ_BIT(PORTC, PORTC5)); // Writing the negated state of pin A5 to pin 13
  }
}