int mojcas = 0;
void setup() {
  Serial.begin(9600);
pinMode(13, OUTPUT);

}

void loop() {
delay(1);
mojcas = mojcas + 1;
Serial.println(mojcas);

if (mojcas == 300) digitalWrite(13, HIGH);

if (mojcas == 600) {digitalWrite(13,LOW);
  mojcas = 0;
}


}