#include<Servo.h>
Servo servo;
int echopin = 3;
int trigpin = 4;


void setup() {
  pinMode(echopin, INPUT);
  pinMode(trigpin, OUTPUT);
  servo.attach(9);

}

void loop() {
  digitalWrite(trigpin, HIGH);

  delay(15);

  digitalWrite(trigpin, LOW);

  int durata = pulseIn(echopin, HIGH);
  int distanza = 0.034 * durata /2;
  if(distanza < 20){
    servo.write(0);

  }

  else{
    servo.write(90);
  }
}