const int trigPin = 7;
const int echoPin = 6;
const int buzzPin = 5;
const int ledPin = 4;

long duration;

long microsecondsToCentimeters(long microseconds) {
   return microseconds / 29 / 2;
}

void setup() {
  Serial.begin(9600);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(ledPin, OUTPUT);
}

void loop() {
   long duration, cm;
   pinMode(trigPin, OUTPUT);
   digitalWrite(trigPin, LOW);
   delayMicroseconds(2);
   digitalWrite(trigPin, HIGH);
   delayMicroseconds(10);
   digitalWrite(trigPin, LOW);
   pinMode(echoPin, INPUT);
   duration = pulseIn(echoPin, HIGH);
   cm = microsecondsToCentimeters(duration);
   Serial.print(cm);
   Serial.print("cm");
   Serial.println();
   delay(100);

   digitalWrite(ledPin, HIGH); //here i need to do something with if and else but i dont know how
   digitalWrite(buzzPin, HIGH);

}