int greenLed1 = 2;  
 int redLed1 = 3;    
 int yellowLed1 = 4; 
 int greenLed2 = 5; 
 int redLed2 = 6;   
 int yellowLed2 = 7; 
void setup() {
 
  pinMode(greenLed1, OUTPUT);
  pinMode(redLed1, OUTPUT);
  pinMode(yellowLed1, OUTPUT);
  pinMode(greenLed2, OUTPUT);
  pinMode(redLed2, OUTPUT);
  pinMode(yellowLed2, OUTPUT);
}

void loop() {
  
  digitalWrite(greenLed1, HIGH);
  digitalWrite(redLed1, LOW);
  digitalWrite(yellowLed1, LOW);
  
  digitalWrite(greenLed2, LOW);
  digitalWrite(redLed2, HIGH);
  digitalWrite(yellowLed2, LOW);
  
  delay(2000);

  digitalWrite(greenLed1, LOW);
  digitalWrite(redLed1, LOW);
  digitalWrite(yellowLed1, HIGH);
  
  digitalWrite(greenLed2, HIGH);
  digitalWrite(redLed2, LOW);
  digitalWrite(yellowLed2, LOW);
  
  delay(1000);
  
   digitalWrite(greenLed1, LOW);
  digitalWrite(redLed1, HIGH);
  digitalWrite(yellowLed1, LOW);
  
  digitalWrite(greenLed2, LOW);
  digitalWrite(redLed2, LOW);
  digitalWrite(yellowLed2, HIGH);
  
  delay(3000);
  }