First off, the "I" at the beginning of the sentence isn't capitilized. The first letter of the first word of a sentence is always capitalized. Also, there is an apostrophe between the "n" and "t" of don't. Next, the words "what" and "this" shouldn't be together they are two separate words. Last, the wrong form of punctuation is used, they are making a statement not an exclamation. So you would use a period. Hope this helps.
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