#include <Servo.h>
Servo servo;
const int trig = 13;
const int echo = 12;
long duration;
int distance;


void setup() {
  servo.attach(11);
  pinMode(trig, OUTPUT);
  pinMode(echo, INPUT);
  servo.write(0);
}

void loop() {
  digitalWrite(trig, LOW);
  delay(20);
  digitalWrite(trig, HIGH);
  delay(100);
  digitalWrite(trig, LOW);

  duration = pulseIn(echo,HIGH);
  distance = (duration * 0.0343) / 2;
  delay(1000);

  if (distance <= 50) {
    servo.write(90);
    delay(2000);
  }

  servo.write(0);
  delay(2000);

  

}