int light_sensor = A3;
void setup()
 {
  // put your setup code here, to run once:
  Serial.begin(9600);
}
void loop()
{
  // put your main code here, to run repeatedly:
  int raw_light = analogRead(light_sensor);

  int light = map (raw_light, 0 ,1023 , 0 , 100 );
  Serial.print("Light level: ");
  Serial.println(light);
  delay(1000);
}