Solve the CodeSprint4 Leibniz code golf challenge in Python in 66 characters

Question

Check out this challenge:

https://www.hackerrank.com/codesprint4/challenges/leibniz

(The competition has already ended, so I'm just curious about the Python solution, which the organizers refused to reveal, so this is not cheating in any way.)

I only managed to solve the challenge in 77 characters. (Talking only about Python here.) However, one adr2370 managed to solve the challenge in 66 characters!

Please help me find the 66-character solution! I'm very very curious because I had to work really hard to bring mine down to 77, and I'm amazed as to how someone came up with a 66-character solution.

For reference, my solution:

for j in'x'*input():print'%.15f'%sum((-1)**i/(2.*i+1)for i in range(input()))

Answer 1

Python 71 bytes

exec"print'%.15g'%sum((-1.)**i/(i-~i)for i in range(input()));"*input()

Not quite 66 bytes, but with a score of 22.90, it would have ranked second overall.

Edit: regarding Ari's comment about the 66 byte Python solution being a 'hack', I don't think that's exactly what happened. I've noticed several times that the submitted language is displayed incorrectly. For example here: Baconian Cipher. This challenge may only be submitted in Brainf_ck, yet the second ranked solution was submitted in Python 2 (interestingly enough, spot 23 is also Python 2. If I were to speculate, I would say that if the language information is missing from a submission for whatever reason, it seems to default to Python).

I suspect that a similar error may have occurred here, and that the shortest Python solution submitted during the challenge was actually 72 bytes.

Update: After speaking with a moderator, it seems that Ari was right: