PokerStars No-Limit Hold'em, $0.25 BB (6 handed) Poker-Stars Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

CO ($82.50)
Button ($43.60)
Hero ($27.55)
BB ($34.40)
UTG ($26.40)
MP ($60)

Preflop: Hero is SB with A, K.
UTG raises to $1, 1 fold, CO calls $1, Button raises to $3, Hero ???

What would be the correct move here?