#include <Servo.h>

Servo servo;
const int trigPin = 9;
const int echoPin = 10;
const int redLed = 2;
const int yellowLed = 3;
const int greenLed = 4;

void setup() {
  servo.attach(11);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(redLed, OUTPUT);
  pinMode(yellowLed, OUTPUT);
  pinMode(greenLed, OUTPUT);
  servo.write(0);
}

void loop() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  long duration = pulseIn(echoPin, HIGH);
  int distance = duration * 0.034 / 2;

  if (distance < 10) {
    digitalWrite(redLed, HIGH);
    digitalWrite(yellowLed, LOW);
    digitalWrite(greenLed, LOW);
    servo.write(90);
  } else if (distance < 20) {
    digitalWrite(redLed, LOW);
    digitalWrite(yellowLed, HIGH);
    digitalWrite(greenLed, LOW);
    servo.write(45);
  } else {
    digitalWrite(redLed, LOW);
    digitalWrite(yellowLed, LOW);
    digitalWrite(greenLed, HIGH);
    servo.write(0);
  }
  delay(100);
}