Alyssa has four marbles: a red one, a blue one, a green one, and a yellow one. In how many different ways can she form a set consisting of some of the marbles if she must choose at least one marble?  (In a set of chosen marbles, it does not matter in what order she chose the marbles.)
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Alyssa has four marbles: a red one, a blue one, a green one, and a yellow one. In how many different ways can she form a set consisting of some of the marbles if she must choose at least one marble?  (In a set of chosen marbles, it does not matter in what order she chose the marbles.)
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
15
Alyssa has four marbles: a red one, a blue one, a green one, and a yellow one. In how many different ways can she form a set consisting of some of the marbles if she must choose at least one marble?  (In a set of chosen marbles, it does not matter in what order she chose the marbles.)
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