/* A high school has a new principal. On
/* his first day he had his students
/* perform an opening day ceremony.
/* There are 1000 lockers and 1000
/* students in the school. The principal
/* asks the first student to go to every
/* locker and open it. Then he asks the
/* second student to go to every second
/* locker (even #) and close it. He has
/* the third student go to every third
/* locker and open it if it's closed and
/* close it if it's open. He has the fourth
/* student do this to every fourth locker
/* and so on. After the process is completed
/* with the 1000th student how many lockers
/* are open?

alanna [

 int la(1000),i,ln,tot /* locker array, index, locker number, total

 pl "alanna2.tc - tct - 9/30/2016";pl "";pl ""

 for (ln=1;ln<=1000;++ln) [
  for (i=ln;i<=1000;i=i+ln) [
   la(i)=1-la(i) /* toggle locker state
  ]]

 for (i=1;i<=1000;++i) [
  if (la(i)==1) [ /* if open, display and tally 
   pn i;++tot
   if (i%10==0) pl ""
  ]]

 pl "";pl "";pn tot;ps " lockers are open.";pl ""

 ]