How to define I/O pins in if condition

I want to define I/O pins depending on the model I define at the start.
let's consider I define model as A

#define MODEL "A"

then I want my input pins to be

#define IN1 12
#define IN1 14
#define IN1 16

And if I define model as B then I want to define pins differently. How can I do it?
I tried using #ifdef or #if but not sure how to use it properly. Any help is appreciated.

Your post was MOVED to it's current location as it is more suitable.

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Take a look at #ifdef by means of which you can check whether something is #defined and then conditionally #define more values

At its most basic, but there is much more that you can do

#define typeA

#ifdef typeA
  #define X 123
#endif

#ifdef typeB
  #define X 456
#endif

void setup()
{
  Serial.begin(115200);
  while (!Serial);
  Serial.println(X);
}

void loop()
{
}

The preprocessor understands if too, I've seen this over and over.

#if ARDUINO >= 100
#include "Arduino.h"
#else
#include "WProgram.h"
#endif
//#define model_A
#define model_B

#ifdef model_A
#define IN1 12
#define IN2 14
#define IN3 16
#endif

#ifdef model_B
#define IN1 2
#define IN2 4
#define IN3 6
#endif

void setup()
{
   Serial.begin(115200);
   Serial.print("pin definitions   IN1 ");
   Serial.print(IN1);
   Serial.print("  IN2 ");
   Serial.print(IN2);
   Serial.print("  IN3 ");
   Serial.println(IN3);
}

void loop()
{
}

Bob beat me to it but this is a bit different.

Thank you for the reply. Problem is solved.