PROBLEM STATEMENT
A hallway is filled with lockers numbered 1 through N, initially all closed.  Out of boredom, Dave 
and Earl decide to open all the lockers.  They make multiple passes through the hallway, each 
beginning at locker 1.  On the first pass, they open the first unopened locker, and every second 
unopened locker thereafter.  On the second pass, they open the first unopened locker, and every 
third unopened locker thereafter.  In general, on the nth pass, they open the first unopened 
locker, and every (n+1)th unopened locker thereafter.

For example, with 9 lockers, on the first pass they open 1, 3, 5, 7, and 9, leaving 2, 4, 6, and 
8.  On the second pass they open 2 and 8, leaving 4 and 6.  On the third pass they open locker 4, 
and on the final pass locker 6.

You will be given N, the number of lockers.  Return the number of the locker opened last.

DEFINITION
Class:LockersDivOne
Method:lastOpened
Parameters:int
Returns:int
Method signature:int lastOpened(int N)


CONSTRAINTS
-N will be between 1 and 2000000, inclusive.


EXAMPLES

0)
9

Returns: 6

The example from the problem statement.

1)
42

Returns: 42



2)
314

Returns: 282



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