int red = 9;
int yellow = 8;
int green = 7;
void setup() {
  // put your setup code here, to run once:
pinMode(red, OUTPUT);
pinMode(yellow, OUTPUT);
pinMode(green, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
digitalWrite(red, LOW);
digitalWrite(green, HIGH);
delay(20000);

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

digitalWrite(yellow, LOW);
digitalWrite(red, HIGH);
delay(17000);
}