int state;

void setup() {
  pinMode(D0, OUTPUT);// initialize digital pin LED_BUILTIN as an output
  pinMode(D1, INPUT);

}

void loop() {
  // put your main code here, to run repeatedly:
state=digitalRead(D1);// Variable for certain values
  if(state==HIGH)
  {
    digitalWrite(D0,HIGH); //Turns the LED ON (HIGH voltage level)
  }
  else{
    digitalWrite(D0,LOW); //Turns the LED OFF (LOW voltage level)
  }
}