def split(t,n=1990):
    out=[];op=False
    while t:
        pre="```\n" if op else "";room=n-len(pre)-4
        if len(t)<=room:out.append(pre+t);break
        cut=t.rfind("\n",0,room);cut=cut if cut>room//2 else room
        chunk=t[:cut];t=t[cut:].lstrip("\n")
        o=op^(chunk.count("```")%2==1)
        out.append(pre+chunk+("\n```" if o else ""));op=o
    return out or [""]