#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>

#undef F_CPU 
#define F_CPU 80000000

long s = 0;

//Interrupt subroutine for Timer0 Overflow interrupt
ISR(TIMER0_OVF_vect) 
{
	PORTD ^= (1 << PD1); //Toggle PD1
	s++;
} 

int main(void)
{
	DDRD |= (1 << PD1)|(1 << PD2); //LED 1 and 2
         
    //Timer 0  
    TCCR0= (1<<CS02)|(1<<CS00); //Start Timer 0 with prescaler 1024
    TIMSK= (1<<TOIE0);          //Enable Timer 0 overflow interrupt
    
    PORTD &= ~(1 << PD1); //LED 1 ON  
    PORTD &= ~(1 << PD2); //LED 2 ON     
    _delay_ms(100);
    PORTD |= (1 << PD1); //LED 1 OFF
    PORTD |= (1 << PD2); //LED 2 OFF
        
    sei();         
    
	for(;;)
    {
		if(s > 100)
		{
			PORTD &= ~(1 << PD2); //LED 2 ON     
		}
    }
	return 0;
}