// Number of LEDs
const int numLEDs = 10;

// Array to store pin numbers
int ledPins[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

void setup() {
  // Set all LED pins as OUTPUT
  for (int i = 0; i < numLEDs; i++) {
    pinMode(ledPins[i], OUTPUT);
  }
}

void loop() {
  // Turn off all LEDs
  for (int i = 0; i < numLEDs; i++) {
    digitalWrite(ledPins[i], LOW);
    delay(50);
  }


  // Turn on all LEDs
  for (int i = 0; i < numLEDs; i++) {
    digitalWrite(ledPins[i], HIGH);
    delay(50);
  }
}