800. Similar RGB Color

In the following, every capital letter represents some hexadecimal digit from 0 to f .

The red-green-blue color "#AABBCC"  can be written as  "#ABC" in shorthand.  For example, "#15c" is shorthand for the color "#1155cc" .

Now, say the similarity between two colors "#ABCDEF" and "#UVWXYZ" is -(AB - UV)^2 - (CD - WX)^2 - (EF - YZ)^2 .

Given the color "#ABCDEF" , return a 7 character color that is most similar to #ABCDEF , and has a shorthand (that is, it can be represented as some "#XYZ"

Example 1:

Input:

 color = "#09f166"
Output:

 "#11ee66"
Explanation: 

 
The similarity is -(0x09 - 0x11)^2 -(0xf1 - 0xee)^2 - (0x66 - 0x66)^2 = -64 -9 -0 = -73.
This is the highest among any shorthand color.

Note:

• color is a string of length 7 .
• color is a valid RGB color: for i > 0 , color[i] is a hexadecimal digit from 0 to f
• Any answer which has the same (highest) similarity as the best answer will be accepted.
• All inputs and outputs should use lowercase letters, and the output is 7 characters.