Given a sorted array of quote timestamps quote_ts with prices quote_px, return one price per trade timestamp in trade_ts:

• take the price of the most recent quote with quote_ts <= trade_ts
• yield np.nan when no quote precedes the trade

Input

trade_ts = [1 4 5 0]
quote_ts = [2 4 6]
quote_px = [10. 20. 30.]

Output

[nan 20. 20. nan]