const int Trigpin=4;// #difine Trigpin 4
const int Echopin=2;// #difine Echopin 2
long duration;
int distance;
#define RLED 16
#define GLED 17
#define BUZ 18

void setup()
{
  Serial.begin(9600);
  pinMode(Trigpin, OUTPUT);
  pinMode(Echopin, INPUT);
  pinMode(RLED, OUTPUT);
  pinMode(GLED, OUTPUT);
  pinMode(BUZ, OUTPUT);
}

void loop()
{
  digitalWrite(Trigpin, LOW);
  delayMicroseconds(2);
  digitalWrite(Trigpin, HIGH);
  delayMicroseconds(10);
  digitalWrite(Trigpin, LOW);

  duration = pulseIn(Echopin, HIGH);
  distance=duration*0.034/2;
  Serial.print("Dist:");
  Serial.print(distance);
  Serial.println(" cm");

  if(distance<100)
  {
    digitalWrite(RLED,HIGH);
    digitalWrite(GLED,LOW);
    digitalWrite(BUZ,HIGH);
  }
  else
  {
    digitalWrite(RLED,LOW);
    digitalWrite(GLED,HIGH);
    digitalWrite(BUZ,LOW);
  }
}