void setup (){
  pinMode(16,OUTPUT);
  pinMode(17,OUTPUT);
  pinMode(18,OUTPUT);
}

void loop() {
  digitalWrite(16,HIGH);
  digitalWrite(17,LOW);
  digitalWrite(18,LOW);
  delay(5000);
  digitalWrite(16,LOW);
  digitalWrite(17,HIGH);
  digitalWrite(18,LOW);
  delay(2000);
  digitalWrite(16,LOW);
  digitalWrite(17,LOW);
  digitalWrite(18,HIGH);
  delay(5000);
}