everyone change the light once when they get out but if one person has go out once, just keep the light don't change anything...tvb now,tvbnow,bttvb) p3 ]5 k+ {8 K
if the light turn on and off for 100 times, all people have been go out...
I think everybody just go to the yard but not go back to the cell, therefore everyday theres one new person going to the yard. and after 100 days everybody will be in the yard.