ATtiny13 timer + interrupt

#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/sleep.h>

#define LED0 0
#define LED4 4
#define SWITCH3 3

volatile int hodnota=0;

int main (void)
{
   DDRB |= (1 << LED0);  // definujem vystupny port pre LED
   DDRB |= (1 << LED4);  // definujem vystupny port pre LED
   DDRB &= ~(1 << SWITCH3);  // nastavujem vstup pre tlacitko
   PORTB |= (1 << SWITCH3);  //aktivujem pull-up

   GIMSK |= _BV (PCIE);   // Povolenie externych preruseni
   PCMSK |= (1<<PCINT3);

   TCCR0A |= (1<<WGM01); // Casovac do CTC modu
   TIMSK0 |= (1<<OCIE0A); // Povolenie CTC prerusenia
   TCCR0B |= ((1 << CS02) | (1 << CS00));  // spomalenie CLOCK/1024
   OCR0A = 0xFD;  //hodnota do casovaca
   sei();

   while (1) {
     set_sleep_mode(SLEEP_MODE_IDLE);
     sleep_mode();
     }
} 

ISR(TIM0_COMPA_vect)
{
  //predlzenie casoveho intervalu 10x
  if (hodnota++ > 10) {
    PORTB ^= (1 << LED0); // LED on/off
    hodnota=0;
    // ak svieti LED aktivovana tlacitkom, zhasnem ju
    PORTB &= ~(1 << LED4);
    }
} 

//stlacene tlacitko, rozsvietim LED
ISR(PCINT0_vect)
{
  PORTB |= (1 << LED4);
}