You deal and pass, the auction ends with RHO bidding 3NT. Playing 3/5 leads and udca + o/e discards, you lead a small ♦ and the defence proceeds as follows:
T1: ♦3-♦2-♦J-♦A
T2: ♣A-♠2-♣2-♣7
T3: ♣Q-♥4-♣4-♣K
T4: ♦8-♦K-♦5-♦9
T5: ♣8-♠6-♣J-♣T
T6: ♣9-♠9-♣3-?
You have to discard and this is the position:
Scoring: XIMP
Pass-(Pass)-1♣ - (X)
1♥ - (Pass)-Pass-(3NT)
Pass-(Pass)-1♣ - (X)
1♥ - (Pass)-Pass-(3NT)

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Pass-(Pass)-1♣ - (X)
1♥ - (Pass)-Pass-(3NT)