Relationship between ramps pins and arduino mega's pins

Hi,
I've been working on a 3d printer and i've come to the last step, which is wiring it all up.
the 3d printer I'm making is ONLY with the arduino mega. No ramps. If I need to get ramps later , I will, but for now, can someone please help me understand which of the ramps pin goes with which arduino pin. For example, in the repetier firmware, the code is like this:
#define X_STEP_PIN 54
#define X_DIR_PIN 55
#define X_ENABLE_PIN 38
#define X_MIN_PIN 3
#define X_MAX_PIN 2

But arduino doesn't have a 54 and a 55 pin. I've been googling this and i found that ramps pins 54 - 69 are the same as pins A0 - A15 on the arduino mega.
I know this but not for the other pins...
Can someone please tell me the connection of all the ramps pins to the arduino pins?
like: pin 54 on ramps = A0 on arduino. I need this for all of the pins.
Thank you so much for your time, Mitch.

Thr schematic has the pin layout
[reprap.org]