23.数列{an}\{a_{n}\}{an}的前nnn项和为SnS_{n}Sn,且an=(−1)n(2n−1)a_{n}=(-1)^{n}(2n-1)an=(−1)n(2n−1),则S2023=S_{2023}=S2023=___−2023-2023−2023___.