int ledRed = 13;
int ledYellow = 10;
int ledGreen = 7;
void setup() {
pinMode(ledRed, OUTPUT);
pinMode(ledYellow, OUTPUT);
pinMode(ledGreen, OUTPUT);
digitalWrite(ledRed, LOW);
digitalWrite(ledYellow, LOW);
digitalWrite(ledGreen, LOW);
}

void loop(){
digitalWrite(ledRed, HIGH);
digitalWrite(ledYellow, LOW);
digitalWrite(ledGreen, LOW);
delay(500);
digitalWrite(ledRed, LOW);
digitalWrite(ledYellow, HIGH);
digitalWrite(ledGreen, LOW);
delay(500);
digitalWrite(ledRed, LOW);
digitalWrite(ledYellow, LOW);
digitalWrite(ledGreen, HIGH);
delay(500);
}