int red=9;
int yellow=8;
int green=7;

void setup() {
  pinMode(red,OUTPUT);
  pinMode(yellow,OUTPUT);
  pinMode(green,OUTPUT);
}

void loop() {
  digitalWrite(red,HIGH);
  digitalWrite(yellow,LOW);
  digitalWrite(green,LOW);
  delay(3000);

  digitalWrite(red,LOW);
  digitalWrite(yellow,HIGH);
  digitalWrite(green,LOW);
  delay(2000);

  digitalWrite(red,LOW);
  digitalWrite(yellow,LOW);
  digitalWrite(green,HIGH);
  delay(3000);

  digitalWrite(red,HIGH);
  digitalWrite(yellow,HIGH);
  digitalWrite(green,HIGH);
  delay(2000);

  digitalWrite(red,LOW);
  digitalWrite(yellow,LOW);
  digitalWrite(green,LOW);
  delay(2000);
}