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

const int redDuration=5000;
const int greenDuration=2000;
const int yellowDuration=5000;

void setup() {
  // put your setup code here, to run once:
  pinMode(redPin, OUTPUT);
  pinMode(yellowPin, OUTPUT);
  pinMode(greenPin, OUTPUT);

}

void loop() {
  //red
  digitalWrite(redPin, HIGH);
  digitalWrite(greenPin, LOW);
  digitalWrite(yellowPin, LOW);
  delay(redDuration);

  //yellow
  digitalWrite(yellowPin, HIGH);
  digitalWrite(greenPin, LOW);
  digitalWrite(redPin, LOW);
  delay(yellowDuration);

  //green
  digitalWrite(greenPin, HIGH);
  digitalWrite(redPin, LOW);
  digitalWrite(yellowPin, LOW);
  delay(greenDuration);

}