void setup() {
  // put your setup code here, to run once:
pinMode(3,OUTPUT);
pinMode(A0,INPUT);
Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
 int x=analogRead(A0);
 Serial.println("x: ");
 Serial.println(x);

 int y=map(x,0,1023,0,255);
 Serial.println("y: ");
 Serial.println(y);
 analogWrite(3,y);
 delay(1000);
}