#define TRIG 2
#define ECHO 3
const int RED = 11;
const int YELLOW = 10;
const int GREEN = 9;

void setup(void) {
  // put your setup code here, to run once:
  Serial.begin(9600);;
  pinMode(TRIG, OUTPUT);
  pinMode(ECHO, INPUT);
  pinMode(RED, OUTPUT);
  pinMode(YELLOW, OUTPUT);
  pinMode(GREEN, OUTPUT);
}

float Read_Distance() {
  digitalWrite(TRIG, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG, LOW);
  int duration = pulseIn(ECHO, HIGH);
  return duration * 0.034 / 1.97626;
}

void loop() {
  
  
  Serial.print("Measured distance: ");
  Serial.println(Read_Distance());

  delay(100);

  float Distance = Read_Distance();
  float TRUE = Distance <= 100;
  
  
  if (digitalRead(Distance) == TRUE) {
    digitalWrite(GREEN, LOW);
    digitalWrite(YELLOW, HIGH);
    delayMicroseconds(3e+6);
    digitalWrite(YELLOW, LOW);
    digitalWrite(RED, HIGH);
    delayMicroseconds(8e+6);
    digitalWrite(GREEN, HIGH);

  }else
    digitalWrite(RED, LOW);
    digitalWrite(YELLOW, LOW);
    digitalWrite(GREEN, HIGH);

}