[Solved] Random function without read the Analog 0

I need to generate a random value between 1 and x, but my project already use all the analog pin so I can't use this page:

http://arduino.cc/en/Reference/random

What can I do? I was thinking to implement a software LFSR.

Are you saying the analogue pins are in use as digital pins, and that's the reason you can't use them? Normally, you only ever call the seed function once, so this could be done in setup.

I use them to check whenever a user press a push button.

I defined them in this way

#define Power   A0
#define Select  A1
#define Up  A2
#define Down    A3    
#define Left    A4
#define Right   A5

and in setup()

  //Setup the Joystick buttons as inputs
    pinMode(Power, INPUT);
    pinMode(Up, INPUT);
    pinMode(Down, INPUT);
    pinMode(Left, INPUT);
    pinMode(Right, INPUT);
    pinMode(Select, INPUT);

  //Enable pullups on Joystick buttons
    digitalWrite(Power, HIGH);
    digitalWrite(Up, HIGH);
    digitalWrite(Down, HIGH);
    digitalWrite(Left, HIGH);
    digitalWrite(Right, HIGH);
    digitalWrite(Select, HIGH);

and using 6 push buttons between GND and each analog input. My project is a MP3 player

So, use them as the random seed before you use them as digital pins.

I was confusing how the random function works. It just need to take a first value only one time, not every time that it is called, isn't it?

Thank you so much AWOL

The random function is a pseudo random number generator, a complex mathematical function returning randomly spread numbers over a range. Because every new number is calculated based on the previous it has to be initialized at some point (called seeding). For the seeding it's best to use some truly random value as it is the noise on a not connected analog input.

Thanks pylon, now it's definitely clear.