#include <Servo.h>

const int BTN_PIN = 3;
const int SERVO_PIN = 11;

Servo servo;

void setup() {
  Serial.begin(115200);
  pinMode(BTN_PIN, INPUT_PULLUP);
  servo.attach(SERVO_PIN);
  servo.write(90);
}

void loop() {
  if (digitalRead(BTN_PIN) == LOW)  {
    for (int count = 0; count < 5; count++) {
      servo.write(0);
      delay (500);
      servo.write(90);
      delay(500);
    }
  }
}