#include <Servo.h>

Servo myservo; 

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

void loop() 
{ 
myservo.write(90); 
delay(1000); 
myservo.write(180); 
delay(1000);
myservo.write(180); 
delay(1000);
myservo.write(0); 
delay(1000);
}