Given integers $a_1, \ldots, a_n, n \in \mathbb{N}$$a_1, \ldots, a_n, b \in \mathbb{N}$. What is the complexity of the following problem $$ \exists x_1, \ldots, x_n \in \mathbb{N} \text{ such that } a_1x_1 + \ldots a_nx_n = b? $$ I can't find this subset-sum variant in the literature.