const int red = 10;
const int ylw = 9;
const int grn = 8;

void clear() {
  digitalWrite(red, 0);
  digitalWrite(ylw, 0);
  digitalWrite(grn, 0);
}

void setup() {
  pinMode(red, OUTPUT);
  pinMode(ylw, OUTPUT);
  pinMode(grn, OUTPUT);
  clear();
}

void loop() {
  
  digitalWrite(grn, 1);
  delay(5000);
  digitalWrite(grn, 0);
  digitalWrite(ylw, 1);
  delay(3000);
  digitalWrite(ylw, 0);
  digitalWrite(red, 1);
  delay(5000);
  digitalWrite(red, 0);
}