int trig = 2;
int echo = 3;
int led = 13;
int led2 = 12;
int led3 = 11;


void setup() {
  pinMode(trig, OUTPUT);
  pinMode(echo, INPUT);
  pinMode(led, OUTPUT);
}

void loop() {
  digitalWrite(trig, LOW);
  delayMicroseconds(2);

  digitalWrite(trig, HIGH);
  delayMicroseconds(10);

  digitalWrite(trig, LOW);

 long duration = pulseIn(echo, HIGH);
  // Calculating the distance

int dist = duration * 0.034/2;
  if(dist <= 25){
    digitalWrite(led, HIGH);
    digitalWrite(led2, LOW);
    digitalWrite(led3, LOW);

  }

  else if(dist <= 50){
    digitalWrite(led2, HIGH);
    digitalWrite(led, LOW);
    digitalWrite(led3, LOW);

  }
  else if(dist <= 100){
    digitalWrite(led3, HIGH);
    digitalWrite(led, LOW);
    digitalWrite(led2, LOW);

  }
  else{
    digitalWrite(led, LOW);
    digitalWrite(led3, LOW);
    digitalWrite(led2, LOW);
  }
}