int leds[] = {13, 11, 9 ,7, 5, 3};

void readyleds(int leds[], int siz)
{
  for (int i = 0; i < siz; i++)
  {
    pinMode(leds[i], OUTPUT);
    pinMode(leds[i] - 1, OUTPUT);

    digitalWrite(leds[i], HIGH);
    digitalWrite(leds[i] - 1, HIGH);
  }

  Serial.begin(9600);
}

void setled(int index, bool value, int leds[])
{
  digitalWrite(leds[index] - 1, value ? LOW : HIGH);
}

void clearleds(int leds[], int siz)
{
  for (int i = 0; i < siz; i++)
    setled(i, false, leds);
}

void setup()
{
  readyleds(leds, (sizeof leds / sizeof leds[0]));
  pinMode(A0, INPUT);
}

void loop()
{
  clearleds(leds, (sizeof leds / sizeof leds[0]));

  Serial.print(analogRead(A0));
  Serial.print("\n");
}