How to find generator matrix given a PCM of a Hamming code?

Question

I'm having trouble as how to begin solving this. I'm given a Hamming Parity Check Matrix, and I have to find code vector V and generator matrix G.

H = \begin{bmatrix} 0&0&1&1&0&1&1\\ 0&1&0&1&1&0&1\\ 1&0&0&0&0&1&1 \end{bmatrix}

Any explanation would be most welcome, mostly on the Generator matrix part. Thanks in advance.