#define RED_LED 18

#define YELLOW_LED 19

#define GREEN_LED 21

void setup() {

pinMode (RED_LED, OUTPUT);

pinMode (YELLOW_LED, OUTPUT);

pinMode (GREEN_LED, OUTPUT);

}

void loop() {

digitalWrite(GREEN_LED, HIGH);

delay (5000);

digitalWrite(GREEN_LED, LOW); 

digitalWrite(YELLOW_LED, HIGH);

delay (2000);

digitalWrite(YELLOW_LED, LOW);

digitalWrite(RED_LED, HIGH);

delay (2000);

digitalWrite(RED_LED, LOW);

}