int ledPin = 10;

void setup() {
  // put your setup code here, to run once:
  pinMode(LED_BUILTIN, OUTPUT);
  pinMode(ledPin, OUTPUT);
}

void loop() {
  digitalWrite(ledPin, HIGH);
  digitalWrite(LED_BUILTIN, HIGH);
  delay(1000);
  digitalWrite(ledPin, LOW);
  digitalWrite(LED_BUILTIN, LOW);
  delay(1000);
}