#ifndef F_CPU
#define F_CPU 1000000UL
#endif

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

int main(void) {
  DDRB = 0b00000001;

  while (1) {
    PORTB = 0b00000001;
    PORTB = 0b00000000;
  }

  return 0;
}