int echoPin = 2 ;
int trigPin = 3 ;
int led_red = 4 ;
int led_green = 5 ;
int led_blue = 6 ;

void setup() {
  pinMode(echoPin, INPUT);
  pinMode(trigPin, OUTPUT);
  pinMode(led_red, OUTPUT);
  pinMode(led_green, OUTPUT);
  pinMode(led_blue, OUTPUT);
}

float ultrasonic() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  int bounce_duration = pulseIn(echoPin, HIGH);
  return bounce_duration * 0.034 / 2;
}

void loop() {
  float distance = ultrasonic();
  if (distance > 200) {
    digitalWrite(led_blue, HIGH);
    digitalWrite(led_green, LOW);
    digitalWrite(led_red, LOW);
  }
  else if (distance <= 200 && distance > 50) {
    digitalWrite(led_green, HIGH);
    digitalWrite(led_blue, LOW);
    digitalWrite(led_red, LOW);
  }
  else if (distance <= 50) {
    digitalWrite(led_red, HIGH);
    digitalWrite(led_green, LOW);
    digitalWrite(led_blue, LOW);
  }
}