#define PIN_LED 4

void setup() {
  Serial.begin(9600);
  pinMode(PIN_LED, OUTPUT);
  byte a=0;
  do{
    Serial.println(a);
    digitalWrite(PIN_LED, HIGH);
    delay(100);
    digitalWrite(PIN_LED, LOW);
    a++;
    delay(100);
    
  } while (a<5);
}

void loop() {}