Adding decimal point to a string variable

[Tithi]

I have ICD-10 codes without decimal points and I would like to add decimal points after the 3rd character.

For example: 

I have the following:

F3342

F348 

But I would like to have:

F33.42

F34.8

Any help with this will be appreciated! Thank you! 

[A_Kh · Accepted solution]

data have; 
input var $;
cards; 
F3342
F348
;
data want;
	set have; 
	if var ne '' then var= catx('.', substr(var, 1, 3), substr(var, 4)); 
proc print; run;

SUBSTR and CATX functions. 

[Tithi]

Thank you! This worked.