int num = 0;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);

  DDRD &= ~(1<<7);
  PORTD |= (1<<7);
  DDRB &= ~(1<<0);
  PORTB |= (1<<0);
  DDRC &= ~(1<<0);
  PORTC |= (1<<0);
  SREG |= 1<<7;
  PCMSK2 |= 1<<PCINT23;
  PCMSK0 |= 1<<PCINT0;
  PCMSK1 |= 1<<PCINT8;
  PCICR |= 0b0000111;
}

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

}

ISR(PCINT2_vect) //+
  {
    if((PIND&(1<<7)) == 0)
    {
      Serial.println(++num);
    }
  }

ISR(PCINT0_vect) //-
  {
    if((PINB&(1<<0)) == 0)
    {
      Serial.println(--num);
    }
  }

ISR(PCINT1_vect) //R
  {
    if((PINC&(1<<0)) == 0)
    {
      Serial.println(num=0);
    }
  }