int lastClk = 1;
int a = 0;

void setup()  
{
  pinMode(A5, INPUT);
  pinMode(A0, INPUT);
}

void loop() 
{
  if (a < 11 && a >= 0)
  {
    int newClk = digitalRead(A5);
    if (newClk != lastClk) 
    {
      lastClk = newClk;
      int dtValue = digitalRead(A0); 

        if (newClk == LOW && dtValue == HIGH) 
          {
            a ++;
            digitalWrite(a, HIGH);
          }
        else if (newClk == LOW && dtValue == LOW)  
          {
            digitalWrite(a, LOW);
            a --;
          }
    }
  }    
  else if  (a == 11)
  {
    a = 10;
  }
  else if (a == -1)
  {
    a = 0;
  }
}