#define F_CPU 1000000UL
#include <avr/io.h>
#include <util/delay.h>

int main(void){
	while(1){
		for (int i = 1; i<=20; i++){
			for (int i = 1; i<=100; i++){
				PORTD = 0b00000000;
				_delay_us(500);
				PORTD = 0b10000000;
				_delay_us(500);
			}
		}
	}
return 0;
}