void setup() {
  pinMode(15, OUTPUT);  pinMode(5, OUTPUT);
  pinMode(4, OUTPUT);  pinMode(16, OUTPUT);
  pinMode(17, OUTPUT); pinMode(18, OUTPUT);
}
void loop() {
  digitalWrite(15, HIGH);
  delay(100);
  digitalWrite(4, HIGH);
  delay(100);
  digitalWrite(16, HIGH);
  delay(100);
  digitalWrite(17, HIGH);
  delay(100);
  digitalWrite(5, HIGH);
  delay(100);
  digitalWrite(18, HIGH);
  delay(100);
  digitalWrite(15, LOW);
  delay(100);
  digitalWrite(4, LOW);
  delay(100);
  digitalWrite(16, LOW);
  delay(100);
  digitalWrite(17, LOW);
  delay(100);
  digitalWrite(5, LOW);
  delay(100);
  digitalWrite(18, LOW);
  delay(100);
}