const int trig = 33;
const int echo = 25;
const int buzzer = 32;
const int btn = 35;

long duration;
int distance;
int threshold;

void setup() {
pinMode(trig, OUTPUT); 
pinMode(echo, INPUT); 
pinMode(buzzer, OUTPUT);
pinMode(btn, INPUT);

Serial.begin(9600);

}

void loop() {

// Gets the Threshold
int press = digitalRead(btn);
if (press == HIGH){
  threshold = distance;
  Serial.println("press");
}

// Clears the trigPin
digitalWrite(trig, LOW);
delayMicroseconds(2);

// Sets the trigPin on HIGH state for 10 micro seconds
digitalWrite(trig, HIGH);
delayMicroseconds(10);
digitalWrite(trig, LOW);

// Reads the echoPin, returns the sound wave travel time in microseconds
duration = pulseIn(echo, HIGH);

// Calculating the distance
distance= duration*0.034/2;

// Checks the Threshold 
if (distance <= threshold){
  digitalWrite(buzzer, HIGH);
}
else{
  digitalWrite(buzzer, LOW);
}

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

}