#include <Servo.h>

Servo myservo;  // create servo object to control a servo


void setup() {
  myservo.attach(3);  // attaches the servo on pin 9 to the servo object
}

void loop() {
  for(int i=180;i>0;i--){
  myservo.write(i);                
  delay(100);}
  for(int i=0;i<180;i++){
  myservo.write(i);                
  delay(100);}
}