on *:START:{ set %minUsers 5 } ; Replace 6 with the minimum amout of users 
on 1:INVITE:#:{ 
  join $chan 
  timer $+ $chan 1 10 /ckUsers $chan 
} 
alias ckUsers { 
  if $nick($1,0) < %minUsers { part $1 a minimum of %minUsers users are needed for the bot to stay. } 
}