const int LED_PIN = 2;
const int LED1_PIN = 4;
const int LED2_PIN = 19;
void setup() 
{
pinMode (LED_PIN, OUTPUT);
pinMode (LED1_PIN, OUTPUT);
pinMode (LED2_PIN, OUTPUT);
Serial.begin(9600);
}
void loop() 
{
digitalWrite(LED_PIN, HIGH);
digitalWrite(LED1_PIN, LOW);
digitalWrite(LED2_PIN, LOW);
delay(1000);
digitalWrite(LED_PIN, LOW);
digitalWrite(LED1_PIN, HIGH);
digitalWrite(LED2_PIN, LOW);
delay(1000);
digitalWrite(LED_PIN, LOW);
digitalWrite(LED1_PIN, LOW);
digitalWrite(LED2_PIN, HIGH);
delay(1000);
}