void setup() {
  Serial.begin(115200);  
  pinMode(12, OUTPUT);
  pinMode(11, OUTPUT);
  pinMode(3, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(3),toggle,FALLING);
}

void loop() {
  digitalWrite(12, HIGH);
  delay(2000);
  digitalWrite(12, LOW);
  delay(2000);
  

}

volatile int count = 0;

void toggle(){
  count++;
  Serial.print("Count :");
  Serial.println(count);

  boolean state = digitalRead(11);
  digitalWrite(11,!state);
}