void setup() {
  pinMode(A5, OUTPUT);
  pinMode(A4, OUTPUT);
  pinMode(A3, OUTPUT);
  attachInterrupt(digitalPinToInterrupt(2), prerusenie,CHANGE);
  pinMode(2, INPUT_PULLUP);
}

void loop() {
  
  digitalWrite(A5, HIGH);
  delay(500);
  digitalWrite(A5, LOW);
  delay(500);
  digitalWrite(A4, HIGH);
  delay(500);
  digitalWrite(A4, LOW);
  delay(500);
  digitalWrite(A3, HIGH);
  delay(500);
  digitalWrite(A3, LOW);
  delay(500);
}

void prerusenie(){
  digitalWrite(A4, HIGH);
  delay(200);
  digitalWrite(A4, LOW);
  delay(200);
  digitalWrite(A4, HIGH);
  delay(200);
  digitalWrite(A4, LOW);
  delay(200);
}