int echoPin = 22;
int trigPin = 23;
int firstLedPin = 19;
int secondLedPin = 18;
int thirdLedPin = 5;
int fourthLedPin = 17;
int buzzerPin = 16;

void setup() {
  pinMode(echoPin, INPUT);
  pinMode(trigPin, OUTPUT);

  pinMode(firstLedPin, OUTPUT);
  pinMode(secondLedPin, OUTPUT);
  pinMode(thirdLedPin, OUTPUT);
  pinMode(fourthLedPin, OUTPUT);
}

void loop() {
  delay(100);

  digitalWrite(trigPin, HIGH);
  digitalWrite(trigPin, LOW);

  float distance = pulseIn(echoPin, HIGH) * 0.017002 + 0.01;

  digitalWrite(firstLedPin, (distance > 50) ? HIGH : LOW);
  digitalWrite(secondLedPin, (distance > 100) ? HIGH : LOW);
  digitalWrite(thirdLedPin, (distance > 200) ? HIGH : LOW);
  digitalWrite(fourthLedPin, (distance > 300) ? HIGH : LOW);
  tone(buzzerPin, (distance > 300) ? 100 : 0);
}