int pin_dos = 2;
int pin_tres = 3;
int pin_cuatro = 4;
int pin_cinco = 5; 

void setup()
{
  pinMode(pin_dos, OUTPUT);
  pinMode(pin_tres, OUTPUT);
  pinMode(pin_cuatro, OUTPUT);
  pinMode(pin_cinco, OUTPUT);
}
 
void loop()
{
  adelante();
  delay(5000);
  atras();
  delay(5000);
}

void adelante(){
  digitalWrite(pin_dos, LOW);
  digitalWrite(pin_tres, HIGH);
  digitalWrite(pin_cuatro, LOW);
  digitalWrite(pin_cinco, HIGH); 
}

void atras(){
  digitalWrite(pin_dos, HIGH);
  digitalWrite(pin_tres, LOW);
  digitalWrite(pin_cuatro, HIGH);
  digitalWrite(pin_cinco, LOW); 
}