#include <Servo.h>

Servo myservo;

void setup() {
  // put your setup code here, to run once:
  myservo.attach(9);
}

void loop() {
  // put your main code here, to run repeatedly:
  for (int angle = 0; angle <= 180; angle++) {
    myservo.write(angle);
    delay(15);
  }

  for (int angle = 180; angle >= 0; angle--) {
    myservo.write(angle);
    delay(15);
  }
}