int servo_delay = 1500;

void setup() {
  // put your setup code here, to run once:

  pinMode(11,OUTPUT);
  pinMode(10,INPUT);
  pinMode(9,INPUT);
}

void loop() {
  // put your main code here, to run repeatedly:

  digitalWrite(11,HIGH);
  delayMicroseconds(servo_delay);
  digitalWrite(11,LOW);
  delay(18);
  if (digitalRead(10) == HIGH && servo_delay<2000) {
    servo_delay = servo_delay +5;
  }
  if (digitalRead(9) == HIGH && servo_delay>1000) {
    servo_delay = servo_delay -5;
  }

}