const int TRIG_PIN = 2;
const int ECHO_PIN = 4;
long duration, distance;
int a=19,b=18,c=5;
void setup() 
{
Serial.begin(115200);
pinMode(TRIG_PIN, OUTPUT);
pinMode(ECHO_PIN, INPUT);
pinMode(a, OUTPUT);
pinMode(b, OUTPUT);
pinMode(c, OUTPUT);
}
void loop() {
distance = getDistanceInCentimeters();
Serial.println("Distance = "+ String(distance));
delay(1000);
if(distance>=100 && distance<200)
{
  digitalWrite(a, HIGH);
  delay(1000);
}
else
{
  digitalWrite(a, LOW);
}
if(distance>=200 && distance<300)
{
  digitalWrite(a, HIGH);
  digitalWrite(b, HIGH);
  delay(1000);
}
else
{
  digitalWrite(a, LOW);
  digitalWrite(b, LOW);
}
if(distance>=300 && distance<=400)
{
  digitalWrite(a, HIGH);
  digitalWrite(b, HIGH);
  digitalWrite(c, HIGH);
  delay(1000);
}
else
{
  digitalWrite(a, LOW);
  digitalWrite(b, LOW);
  digitalWrite(c, LOW);
}
}
long getDistanceInCentimeters() {
digitalWrite(TRIG_PIN,LOW);
delayMicroseconds(2);
digitalWrite(TRIG_PIN, HIGH);
delayMicroseconds(10);
digitalWrite(TRIG_PIN, LOW);
duration = pulseIn(ECHO_PIN, HIGH);
return (duration * 0.034 / 2) + 1;
}