The question was about getting the input to make a block header hash:
https://blockchain.info/block/0000000000000000000854f801e84750ffa9aaa97e74c36e975df3fa2ad5627c

The idea was to get version, previous block hash, merkle root hash, timestamp, bits and nonce, all in hex and little-endian.

Solution made in python and on URL.

Original writeup (https://github.com/diofeher/ctf-writeups/blob/master/2018-04-15-hackzone/chains.py).