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

void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(red,HIGH);
  digitalWrite(green, LOW);
  delay(30000);
  digitalWrite(green,HIGH);
  digitalWrite(red,LOW);
  delay(30000);
  digitalWrite(green,LOW);
}