def hash_merkle_root(self, merkle_s, target_hash, pos):
        h = hash_decode(target_hash)
        for i in range(len(merkle_s)):
            item = merkle_s[i]
            h = Hash( hash_decode(item) + h ) if ((pos >> i) & 1) else Hash( h + hash_decode(item) )
        return hash_encode(h)