void setup() {
  // put your setup code here, to run once:
pinMode(13, OUTPUT);
digitalWrite(13, HIGH);
pinMode(11, INPUT_PULLUP);
}

void loop() {
  // put your main code here, to run repeatedly:
  if(digitalRead(11)==LOW){
digitalWrite(13, LOW);
delay(200);
digitalWrite(13, HIGH);
delay(100);
  }
}