Two problems in your initial code. First, while ( i < 0 && i > 24 )
. In your test, when will a number ever be less than 0 AND greater than 24 at the same time? BTW, I believe the limit is 23, not 24.
Next, a more subtle issue. You have declared i inside a pair of curly braces, i.e., the do loop. This defines the scope of the variable i. THat means that i doesn't exist outside of those curly braces. If you delcare i before the do loop, so that it is scoped for the entirety of main, your undeclared variable error will go away.
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