void setup()
{
  pinMode(A0, INPUT);
  pinMode(3, OUTPUT);
  Serial.begin(9600);
}

void loop()
{
  int a = analogRead(A0);
  int pwm = map(a, 0, 1023, 0, 255); 

  analogWrite(3, pwm); 

  Serial.print("Value Analog = ");
  Serial.println(a); 
  Serial.print("Value PWM = ");
  Serial.println(pwm); 
  delay(250);
}