#include <stdint.h>

#define DDRA  (*(volatile uint8_t*)0x21)
#define PORTA (*(volatile uint8_t*)0x22)

void delay1sec(void){
    TCNT1 = 0;
    TCCR1A = 0x00;
    TCCR1B = 0x05;

    while (TCNT1 < 15625);

    TCCR1B = 0x00;
}

void setup() {
    DDRA = 0xFF;
}

void port_led(int i){
    PORTA = (1<<i) | (1<<(i+4));
    delay1sec();
    PORTA = 0x00;
    delay1sec();
}

void loop() {
    for(int i = 0; i <= 3; i++){
        port_led(i);
    }
}