Strange Integral Calculation with Traditional Form

I must be doing something wrong.

I define the following integral:
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The code:

!  (
 * SubsuperscriptBox[([Integral]),  ( (- W ) / 2 ),  (W / 2 )] (
 * SubsuperscriptBox[([Integral]),  ( (- L ) / 2 ),  (L / 2 )]a[
    x] [DifferentialD]X  [DifferentialD]Y ) )

… and I get it:W a[x] as a result ??

Should be:

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From a[x] It is an undefined function of x.

EDIT: If I enter it using the "Entry Form" and not the "traditional form":

To integrate[Tointegrate[a[Integrate[to[Integrar[una[Integrate[a[x], {x, -L / 2, L / 2}], {y, -H / 2, H / 2}]

Mathematica understands it, and I get the correct result.

Why is that ?

EDIT 2: putting it in parentheses does not help:

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EDIT 3: Put the parathon around the internal integral, solve the problem, but I do not understand why I have to do that Mathematica should automatically see where the integral starts and ends.

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