def minimaxDepthTLCovers(tlcovs):
    """
    Prune top-level covers for minimax depth
    Inputs:
        tlcovs: A list of top-level covers as returned by explain.
    Outputs:
        tlcovs_xd: The pruned top level covers.
        xd: The minimax depth found.
    """
    xd = max(min(d_min) for (_,_,d_min,_,_) in tlcovs)
    tlcovs_xd = [(u,k,d_min,d_max,ts) for (u,k,d_min,d_max,ts) in tlcovs if min(d_min) == xd]
    return tlcovs_xd, xd