CF1461F Mathematical Expression

Barbara was late for her math class so as a punishment the teacher made her solve the task on a sheet of paper. Barbara looked at the sheet of paper and only saw $ n $ numbers $ a_1, a_2, \ldots, a_n $ without any mathematical symbols. The teacher explained to Barbara that she has to place the available symbols between the numbers in a way that would make the resulting expression's value as large as possible. To find out which symbols were available the teacher has given Barbara a string $ s $ which contained that information. It's easy to notice that Barbara has to place $ n - 1 $ symbols between numbers in total. The expression must start with a number and all symbols must be allowed (i.e. included in $ s $ ). Note that multiplication takes precedence over addition or subtraction, addition and subtraction have the same priority and performed from left to right. Help Barbara and create the required expression!

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The following answers also fit the first example: "2+2+0", "2+2-0", "2\*2+0".