#define ECHO_PIN 11
#define TRIG_PIN 12
#define LED 4

void setup() {
  Serial.begin(9600);
  pinMode(ECHO_PIN, OUTPUT);
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(LED, OUTPUT);
}

void loop() {
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10); 
  digitalWrite(TRIG_PIN, LOW);

  int duration = pulseIn(ECHO_PIN, HIGH);
  int dist = duration / 10;
  Serial.println(dist);
  if (dist > 20) {
    digitalWrite(LED, HIGH);
  }
  delay(1000);
}