int led = 12;
int ldr = A0;
int lux;
void setup() {
  pinMode (led, OUTPUT);
}
void loop() {
  ldr = analogRead (A0);
  lux = map (ldr, 0, 1023, 0, 256);
  if (lux >= 50){
    digitalWrite (led, HIGH);
  }
  else{
    digitalWrite (led, LOW);
  }
}