void setup() {
pinMode(12, OUTPUT);
pinMode(3, INPUT_PULLUP);
Serial.begin(9600);
}

void loop() {
  int x = digitalRead(3);
  if (x==0)
  {
    digitalWrite(12, LOW);
    Serial.println("switch OFF, LED OFF");
  }
  else{
    digitalWrite(12, HIGH);
    Serial.println("switch ON, LED ON");
  }

}