#include <Servo.h>

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

int potpin = A0;  // analog pin used to connect the potentiometer
int val;    // variable to read the value from the analog pin
int pos=0;
void setup() {
  myservo.attach(9);  // attaches the servo on pin 9 to the Servo object
}

void loop() {
for (pos =0; pos<=180; pos+=1){
  myservo.write(pos);
  delay(15); 
}
  for(pos=180; pos>=0; pos-=1){
    myservo.write(pos);
    delay(15);
  }
}