#include  <avr/io.h>

#define F_CPU20000UL
#define THREE_LED PORTA

int main(void){
  DDRA =0x07;// Sets PA2 PA1 PA0 pins as output pins
  while(1){

       THREE_LED  = 0b00000111 ;   // Lights all LEDs
         _delay_ms(1000);        //delay 1 second
      THREE_LED  = 0b00000110 ;  // Lights 2 LEDs
        _delay_ms(1000);        
      THREE_LED  = 0b00000100 ;  
          _delay_ms(1000);
      THREE_LED  = 0b00000000 ;  
          _delay_ms(1000);
      THREE_LED  = 0b00000001 ;  
          _delay_ms(1000);
      THREE_LED  = 0b00000011 ;  
          _delay_ms(1000);
      THREE_LED  = 0b00000010 ;  
          _delay_ms(1000);
      THREE_LED  = 0b00000101 ;  
  }

}