Binary Integer Grammar (allowing leading 0's)

binary-integer
   0
   1
   binary-integer 0
   binary-integer 1
   

Hex Integer Grammar

hex-integer
   0-F
   hex-integer 0-F 
 
0-F
    0
    1
    2
    3
    4
    5
    6
    7
    8
    9
    0
    A
    B
    C
    D
    E
    F
 

How would you modify this to get C hex constants?