const int led= 3;
int potenziometro=A4;
int valLed;
int valPot;
void setup() {
  // put your setup code here, to run once:
pinMode(led, OUTPUT);
pinMode(potenziometro, INPUT);
Serial.begin(9600);
}
void loop() {
  // put your main code here, to run repeatedly:
  valPot=analogRead(potenziometro);
  valLed= map(valPot,0,1023,0,255);
  analogWrite(led,valLed);
}