int ledPin1 = D2;
int ledPin2 = D3;
void setup() {
    // D2 and D3 as output pins
    pinMode(ledPin1, OUTPUT);
    pinMode(ledPin2, OUTPUT);
}

void loop() {
    digitalWrite(ledPin1, HIGH);
    digitalWrite(ledPin2, LOW);
    delay(1000);
    
    digitalWrite(ledPin1,LOW);
    digitalWrite(ledPin2,HIGH);
    delay(1000);
}