void setup() {
  Serial.begin(9600);
  while(!Serial);
  Serial.flush();
  pinMode(3, OUTPUT);
}

void loop(){
  int sensorValue = analogRead(A0);
  int PWM = map(sensorValue, 0, 1023, 0, 255);
  analogWrite(3, PWM);
  
  Serial.print("A0 = ");
  Serial.print(sensorValue);
  
  Serial.print("\tPWM = ");
  Serial.println(PWM);
}