// Ex 3
int pin = 2;
int checkPin ;
void setup() {
  Serial.begin(9600);
  int checkPin = digitalPinToInterrupt(pin);
  if (checkPin == -1) {
    Serial.println("Not a valid interrupt pin!");
  } else {
    Serial.println("Valid interrupt pin.");
}
 
  
}

void loop() 
{
  
}