#define TRIG_PIN 18 
#define ECHO_PIN 5 
#define LED 2
#define LED2 4
float duration_us, distance_cm;

void setup() 
{
  Serial.begin (9600);
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(LED, OUTPUT);
  pinMode(LED2, OUTPUT);
}

void loop() 
{
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
  duration_us = pulseIn(ECHO_PIN, HIGH);
  distance_cm = 0.017 * duration_us;
  if (distance_cm < 30) 
  {
    digitalWrite(LED, HIGH);
  }
  else
  {
    digitalWrite(LED, LOW);
  }
  Serial.print("distanceA: ");
  Serial.print(distance_cm);
  Serial.println(" cm ");
  Blink(LED2);
  delay(500);
}
void Blink(int x)
{
  digitalWrite(x, HIGH);
  delay(10);
  digitalWrite(x, LOW);
}