#include <Servo.h>

Servo myservo;

void setup() {
    myservo.attach(9);
    myservo.write(0);
}

void loop() {
    for (int i = 0; i <= 180; i++) {
        myservo.write(i);
        delay(15);
    }
    for (int j = 180; j >= 0; j--) {
        myservo.write(j);
        delay(15);
    }
}