void setup() {
  pinMode(PA15, OUTPUT);
  pinMode(PB3, OUTPUT);
  pinMode(PB4, OUTPUT);
  pinMode(PB5, OUTPUT);
}

// -------------------- LOOP --------------------
void loop() {
  digitalWrite(PA15,HIGH);
  digitalWrite(PB3,LOW);
  digitalWrite(PB4,LOW);
  digitalWrite(PB5,LOW);
  delay(1000);
  digitalWrite(PA15,HIGH);
  digitalWrite(PB3,HIGH);
  digitalWrite(PB4,LOW);
  digitalWrite(PB5,LOW);
  delay(1000);
  digitalWrite(PA15,LOW);
  digitalWrite(PB3,HIGH);
  digitalWrite(PB4,LOW);
  digitalWrite(PB5,LOW);
  delay(1000);
  digitalWrite(PA15,LOW);
  digitalWrite(PB3,HIGH);
  digitalWrite(PB4,HIGH);
  digitalWrite(PB5,LOW);
  delay(1000);
  digitalWrite(PA15,LOW);
  digitalWrite(PB3,LOW);
  digitalWrite(PB4,HIGH);
  digitalWrite(PB5,LOW);
  delay(1000);
  digitalWrite(PA15,LOW);
  digitalWrite(PB3,LOW);
  digitalWrite(PB4,HIGH);
  digitalWrite(PB5,HIGH);
  delay(1000);
  digitalWrite(PA15,LOW);
  digitalWrite(PB3,LOW);
  digitalWrite(PB4,LOW);
  digitalWrite(PB5,HIGH);
  delay(1000);
  digitalWrite(PA15,HIGH);
  digitalWrite(PB3,LOW);
  digitalWrite(PB4,LOW);
  digitalWrite(PB5,HIGH);
  delay(1000);
}