Revision ac576504-9732-4ff6-b14d-f13dd91ede29 - Code Golf Stack Exchange

#Vim, 59 bytes/keystrokes

 :%s/./&\r/g
 dd:let @q=float2nr(sqrt(line('.')))."gJ@q"
 gg@q

This is almost definitely one of the longest vim answers I have ever posted.