def remove_head_id(ref, hyp):
    """Assumes that the ID is the begin token of the string which is common
    in Kaldi but not in Sphinx."""
    ref_id = ref[0]
    hyp_id = hyp[0]
    if ref_id != hyp_id:
        print(
            """Reference and hypothesis IDs do not match! ref="{}" hyp="{}"
File lines in hyp file should match those in the ref file."""
            .format(ref_id, hyp_id))
        exit(-1)
    ref = ref[1:]
    hyp = hyp[1:]
    return ref, hyp
