const int trigPin = 7;
const int echoPin = 8;
const int buzzer = 13;

void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);

pinMode(3, OUTPUT);
pinMode(4, OUTPUT);
pinMode(5, OUTPUT);
pinMode(buzzer, OUTPUT);

}

void loop() {
  // put your main code here, to run repeatedly:
digitalWrite(trigPin, LOW);
delayMicroseconds(2);
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin,LOW);

long duration = pulseIn(echoPin,HIGH);

int distance = duration * 0.0343/2;

Serial.print("Distance: ");
Serial.print(distance);
Serial.println(" cm");

if (distance>40)
{ digitalWrite(3, HIGH);
digitalWrite(4, LOW);
digitalWrite(5, LOW);
delay(500);
} else if(distance>15)
{ digitalWrite(3, LOW);
digitalWrite(4, HIGH);
digitalWrite(5, LOW);
tone(13,300,25);
delay(500); }
else { 
digitalWrite(3, LOW);
digitalWrite(4, LOW);
digitalWrite(5, HIGH);
tone(buzzer, 626, 250);
delay(500);
}
}