summon falling_block ~ ~.6 ~ {Block:chain_command_block,TileEntityData:{Command:fill ~ ~ ~ ~ ~2 ~ air},Time:1,Passengers:[{id:falling_block,Block:redstone_block,Time:1,Passengers:[{id:falling_block,Block:activator_rail,Time:1,Passengers:[{id:commandblock_minecart,Command:setblock ~1 ~-2 ~ repeating_command_block 1 replace {Command:/scoreboard players add @a join 0,auto:1,TrackOutput:0b}},{id:commandblock_minecart,Command:setblock ~1 ~-1 ~ chain_command_block 1 replace {Command:tellraw @a[tag=!joined]  {"text":"","color":"blue"},auto:1,TrackOutput:0b}},{id:commandblock_minecart,Command:setblock ~1 ~ ~ chain_command_block 1 replace {Command:REPLACE COMMAND WITH ANOTHER OR LEAVE THIS HERE,auto:1,TrackOutput:0b}},{id:commandblock_minecart,Command:setblock ~1 ~1 ~ chain_command_block 1 replace {Command:/scoreboard players tag @a[tag=!joined] add joined,auto:1,TrackOutput:0b}},{id:commandblock_minecart,Command:setblock ~1 ~2 ~ chain_command_block 1 replace {Command:/scoreboard players tag @a[score_join_min=1,tag=joined] remove joined,auto:1,TrackOutput:0b}},{id:commandblock_minecart,Command:setblock ~1 ~3 ~ chain_command_block 1 replace {Command:/scoreboard players set @a[score_join_min=1] join 0,auto:1,TrackOutput:0b}},{id:commandblock_minecart,Command:setblock ~1 ~4 ~ air},{id:commandblock_minecart,Command:/scoreboard objectives add join stat.leaveGame},{id:commandblock_minecart,Command:blockdata ~ ~-3 ~ {Command:,auto:0}},{id:commandblock_minecart,Command:setblock ~ ~-1 ~ command_block 0 1 {auto:1,Command:kill @e[type=commandblock_minecart,r=1]}}]}]}]}