Show me the nearest demon A demonic number is a positive integer whose decimal representation consists of only 6. The list of demonic numbers starts with 6, 66, 666, 6666.

Given a positive integer, output the nearest demonic number. If there are two, output the bigger one.

Testcases:

n   output
1   6
2   6
3   6
6   6
35  6
36  66
37  66
100 66
365 66
366 666
666 666
999 666


This is code-golf. Shortest answer in bytes wins.
Python 2, 28 bytes

lambda n:'6'*len(`-~n*3/11`)