const int pinLED1 = 6;
const int pinLED2 = 7;
const int pinLED3 = 8;

void setup ()
{
  pinMode (pinLED1, OUTPUT);
  pinMode (pinLED2, OUTPUT);
  pinMode (pinLED3, OUTPUT);
}
void loop ()
{
  digitalWrite (pinLED1, HIGH);
  delay(500);
  digitalWrite (pinLED2, HIGH);
  delay(500);
  digitalWrite (pinLED3, HIGH);
  delay(500);
  digitalWrite (pinLED1, LOW);
  digitalWrite (pinLED2, LOW);
  digitalWrite (pinLED3, LOW);
  delay(500);
}