Alternating Sum 1 to N

Read an integer n from standard input and print the alternating sum 1 - 2 + 3 - 4 + ... up to n, with no trailing newline. Odd positions are added and even positions are subtracted. For example, if the input is 4, compute 1 - 2 + 3 - 4, so print:

-2

Use i % 2 to decide whether to add or subtract i.

Expected Output:

-2

Topics:

Loops

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