PokerStars No-Limit Hold'em, $1.00 BB (8 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

UTG ($107.60)
UTG+1 ($14.60)
MP1 ($97)
Hero ($99.50)
CO ($154.20)
Button ($37.50)
SB ($41.20)
BB ($54.65)

Preflop: Hero is MP2 with A, K.
1 fold, UTG+1 raises to $4, 1 fold, Hero ???

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Shortstack is a complete unknown, I just sat down.

What's your move here?