0=13

        0=15

        1=18

        0=19

        0=21

        0=23

        0=25

        1=26

        4a5b7c(10)a(11)b(13)c(15)a(18)b(19)c(21)a(23)b(25)c(26)

        当a=+加法，b=-减法，c=*乘法时：

        4+5-7*(10)+(11)-(13)*(15)+(18)-(19)*(21)+(23)-(25)*(26)=-1253（优先计算乘法）

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