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

  for (int i = 0; i < LED_BUILTIN; i++)
  {
    pinMode(i, OUTPUT);
  }  

}

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

  for (int i = 0; i < LED_BUILTIN; i++)
{
  digitalWrite(i, 1); // zapnuti LED
  delay(100);
  digitalWrite(i, 0); // vypnutí LED diody
}

for (int i = LED_BUILTIN; i > 0; i--)
{
  digitalWrite(i, 1);
  delay(100);
  digitalWrite(i, 0); // vypnutí LED diody
}


}