#include <Servo.h>
Servo myServo;const int trigPin = 9;
const int echoPin = 10; long duration;
int distance;
void setup() {
myServo.attach(11);
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);
Serial.begin(9600);
}

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

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

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

  int angle = map(distance, 0, 50, 0, 180);
  angle = constrain(angle, 0, 180);  // Use constrain, not constraint
  myServo.write(angle);
  delay(100);
}