"hello world"
"ello world"
"llo world"
"lo world"
"hello world"
""
"e"
"el"
""
"l"
""
"l"
"lo"
""
"hello"
""
"abc"
#\h
#\e
#\l
#\o
(#\x #\y #\z)
(#\x)
()