Ok, so there are 4 analog pins, they are all in analog mode.

You are using 2 of them for analog input and want to use 1 for digital output.
That leaves 1 analog pin unaccounted for.

Is that one an OUTPUT too?
It makes a big difference.

If not, and it's just not being used, then you can use HIGH and LOW like normal on the pin with the LED.

If that other pin is also an output, you'll need to use a variable as a Latch (holding reg) to fix the R-M-W issue.
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