I'm trying to grasp the use of functions with the cs50 library to complete the pset1 water task. My code will outright ignore the function I've written, I think this is due to line 10, but what am I missing?

    #include <stdio.h>
    #include <cs50.h>

    //a function that takes 'a', multiplies that by 16 and divides 192 from this
    int convert(int a);

    int main(void)
    {
	    printf("How many minutes do you spend in the shower: ");
	    int a = GetInt();
	
	         if(a <= 0)
	         {
		        printf("You don't shower? Nasty./n");
		        return 0;
	         }
	
	         else
	         {
		     printf("You use %i bottles of water per shower!\n", a);
	         }
    }

             /* Function Argument */
             int convert(int a)
             {
	          return 192/(16*a);
             }
 Many Thanks