#define led_red 2
#define led_yellow 4

void setup() {
Serial.begin(115200);
pinMode(led_red, OUTPUT);
pinMode(led_yellow, OUTPUT);
}

void loop() {

digitalWrite(led_red, HIGH);
delay(3000);
digitalWrite(led_yellow, LOW);
delay(1000);
digitalWrite(led_red, LOW);
delay(3000);
digitalWrite(led_yellow, HIGH);
delay(1000);
Serial.println(led_red);
delay(100);
Serial.println(led_yellow);
delay(100);
}