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

#define DELAY 3

int main ()
{
	DDRB = (1<<PB0) | (1<<PB1) | (1<<PB2) | (1<<PB3);
	PORTB = 0;

	while(1)
	{
		PORTB = (1<<PB0);
		_delay_ms(DELAY);
		PORTB = (1<<PB1);
		_delay_ms(DELAY);
		PORTB = (1<<PB3);
		_delay_ms(DELAY);
		PORTB = (1<<PB2);
		_delay_ms(DELAY);
	}

	return 0;
}