int ledPin = 9;
int buttonPin = 11;

void setup() {
  // put your setup code here, to run once:
  pinMode(ledPin, OUTPUT);
  pinMode(buttonPin, INPUT_PULLUP);
  Serial.begin(115200);
}

void loop() {
  // put your main code here, to run repeatedly:
 if (digitalRead(buttonPin) == LOW)
 digitalWrite(ledPin, HIGH);
 else
 digitalWrite(ledPin, LOW);

}