Turning Off and On a Light with a Photosensor

/*Caroline Sasso*
 * My Program
 * 11/30/2016
 */
 const int PhotoPin=A0;
 int ReadValue=0;
 const int LEDPin=4;

void setup()
{
  pinMode (PhotoPin, INPUT);
  pinMode (LEDPin, OUTPUT);
  Serial.begin(9600);
}
void loop()
{
  ReadValue = analogRead (PhotoPin);
  Serial.println (ReadValue);
  analogWrite (LEDPin, 255-ReadValue*255/103);
}