AOJ 2016 Lifeguard in the Pool

Solved Users (link to submissions)
amano
asi1024
conf
DEGwer
dohatsu
Huziwara
id
ir5
japlj
joisino
laycurse
lx_ambulance
lyrically
namonakiaccount
nel215
not
ogiekako
orpheus
rapi_376
rng_58
runoth
s1220013
satashun
sky58
syl659
tozangezan
uwi
vjudge5
zerokugi
_n_ari