const int monitorPin = 8;  
int lastPinState = HIGH;   
int currentPinState;
void setup() 
{
  pinMode(monitorPin, INPUT_PULLUP);  
  pinMode(12, OUTPUT);

}

void loop() 
{

  currentPinState = digitalRead(monitorPin);

  if (lastPinState == HIGH and currentPinState == LOW) 
  {
    digitalWrite(12,!digitalRead(12));
    delay(50);
  }
  
  lastPinState = currentPinState;
  delay(50);
}