3♣. I expect this auction to bounce quickly, so 1N is out. 2♣ isn't that bad as it's unlikely to be passed out, but then it's hard to get any useful information out of partner as it conveys nothing like this hand. Splintering carries the wrong message about the other red suit, as well as making it very hard to play in clubs. I don't want to play in 3NT, and 5♣ seems too unilateral. While I don't actually expect partner to have a club fit (and 3♣ may make it harder than I'd like to eventually play in the suit), it will tend to get partner to devalue points in the red suits, which seems the best effort that I can make here. Second choice 5♣.