int lastValue;

void setup() {

  Serial.begin(9600);
  Serial.println("BEGIN");
  Serial.println(); 
}

void loop() {

lastValue = (analogRead(A0));

delay(10); // some delay is neede so that the limit values are printed reliably

if (analogRead(A0) != lastValue) {
    Serial.println(analogRead(A0));
}

}