int redPin= 10;
int yellowPin= 9;
int greenPin= 8;

void setup(){
  pinMode(redPin, OUTPUT);
  pinMode(yellowPin, OUTPUT);
  pinMode(greenPin, OUTPUT);
}
void loop(){
  digitalWrite(redPin, HIGH);
  delay(1000);
  digitalWrite(redPin, LOW);

  digitalWrite(greenPin, HIGH);
  delay(1000);
  digitalWrite(greenPin, LOW);

  digitalWrite(yellowPin, HIGH);
  delay(1000);
  digitalWrite(yellowPin, LOW);
}