void setup() {
  pinMode(12, OUTPUT); // led1
  pinMode(13, OUTPUT); // led2
  pinMode(2, INPUT); // knopka
}

void loop() {
  if(digitalRead(2) == 0){
    digitalWrite(12, LOW);
    digitalWrite(13, HIGH); 
  } else {
    digitalWrite(12, HIGH);
    digitalWrite(13, LOW); 
  }
}