Problem with A6 & A7

I am beginner to arduino platform. this my frost post . I'm using arduino nano board. while using analog inputs pin for digital input A0-A5 works great but A6,A7 is not repond with inputs, can any pls tell am i wrong or my board is damaged

code is

void setup()
{
pinMode(13, OUTPUT);
pinMode(A7, INPUT_PULLUP);
}

void loop()
{

if(digitalRead(A6)==LOW)
digitalWrite(13,LOW);
else
digitalWrite(13,HIGH);
}

A6 and A7 are not universal like the other A pins. they are only analog

http://forum.arduino.cc/index.php?topic=152724.0

Thanks ... got it..