int count = 0;

void setup() {
  Serial.begin(9600);
  DDRD &= ~(1<<5);
  PORTD |= (1<<5);

  DDRB &= ~(1<<3);
  PORTB |= (1<<3);

  DDRC &= ~(1<<2);
  PORTC |= (1<<2);

  SREG |= 1<<7;
  PCICR |= 1<<PCIE2;
  PCICR |= 1<<PCIE1;
  PCICR |= 1<<PCIE0;
  PCMSK2 |= 1<<PCINT21;
  PCMSK1 |= 1<<PCINT10;
  PCMSK0 |= 1<<PCINT3;

  Serial.println(count);
}

void loop() {
  // put your main code here, to run repeatedly:

}

ISR(PCINT2_vect)
{
  if((PIND&(1<<5)) == 0)
    {
      count++;
      Serial.println(count);
    }
}
ISR(PCINT1_vect)
{
  if((PINC&(1<<2)) == 0)
    {
      count--;
      Serial.println(count);
    }
}
ISR(PCINT0_vect)
{
  if((PINB&(1<<3)) == 0)
    {
      count = 0;
      Serial.println(count);
    }
}