There are n lights, numbered 1~n. The first person
turns on all the lights, the second person flips all the switches numbered in
multiples of 2 (the lights will be turned off), the third person flips all the
switches numbered multiples of 3 (the lights that are on will be turned off,
the lights that are off will be turned on), and so on. There are a total of k
people, which lights are on at the end? Input: n and k, output the number of
the lights that are on. k=<n<=1000.
Two numbers n and k.
The number of the light that is on.
7 3
1 5 6 7