const int TRIG_PIN = 12;
const int ECHO_PIN = 14;
long duration, distance;
int a=27;
int b=19;
int c=18;
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);
}
else if(distance>=200&distance<=300){
    digitalWrite(a,HIGH);
    digitalWrite(b,HIGH);
}
else{
     digitalWrite(a,HIGH);
     digitalWrite(b,HIGH);
     digitalWrite(c,HIGH);
}
}
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;
}