#include <Arduino.h>

volatile int value = 0;

void setup()
{
  PCICR = 0b00000101;   // turn PCI on Port2 and Port0

  PCMSK0 = 0b00000001;  // Pin 8
  PCMSK2 = 0b00100000;  // Pin 5

  Serial.begin(9600);
}

void loop()
{
  Serial.println(value);
}

ISR(PCINT0_vect)  // Port0 _vect
{
  value++;
}

ISR(PCINT2_vect)  // Port2 _vect
{
  value--;
}