編程高手請進

Please implement the function

 

int isLetter(int n);

 

Allowed operators:  <, &.  

Parentheses are allowed without limit. 
No looping or if statements are allowed.

 

Please minimize the number of operations for efficiency. 最少可以幾次使用以上算符？

 

examples of output:

isLetter(10) = 0, isLetter('&') = 0,
isLetter('A') = 1, isLetter('m') = 1， isLetter(68) = 1 (68 is ascii code for 'D').

 

Hint: 
1. logical true = 1, logical false = 0.  for example (3 > 1) = 1， （3 < 1) = 0.
2. The binary and ascii values for letters are like:

a	097	01100001	A	065	01000001
b	098	01100010	B	066	01000010
c	099	01100011	C	067	01000011
d	100	01100100	D	068	01000100
e	101	01100101	E	069	01000101