void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  pinMode(9, OUTPUT);
  pinMode(3, INPUT);
}

void loop() {
  if (digitalRead(3)) {
    digitalWrite(9, HIGH);
  } else {
    digitalWrite(9, LOW);
  }
  delay(100);
  Serial.println(digitalRead(3));
}