#define F_CPU 1000000UL

#include <avr/io.h>
#include <util/delay.h>

int main() {
  uint8_t x = 0b00000001;
  DDRB = 0b00000001;
  PORTB = 0b00000000;
  while (1) {
    x = (!DDRB && (x)) || (DDRB && (!x));
    PORTB = x;
    _delay_ms(1000);
  }
  return(0);
}