There are 50 people in a room and 50 jars lined up in a straightrow. The first person goes down the?

And takes off every lid of every jar.The second person goes down the row and puts the lid on all the 2s (2 4 6 8 up to 50) the third person does the same either puts on or takes off all the threes (3 6 9)this process continues until all 50 people go. Which jars will be on and which jars will be off ?