Can't save ffmpeg output in Nodejs

I have a problem with saving the preview from the .mp4 file. I followed this tutorial, but I got the Error: ffmpeg exited with code 1: C:\Users\Lenovo\Documents\My projects\YouTube\routes: Permission denied. I don't know how to deal with it, the 'outputPath' is simplestrong text "public/uploads/previews". I am on Windows 10.

return ffmpeg()
            .input(inputPath)
            .inputOptions([`-ss ${startPreviewInSec}`])
            .outputOptions([`-t ${previewDurationInSec}`])
            .noAudio()
            .format("gif")
            .output(outputPath)
            .on("end", resolve)
            .on("error", reject)
            .run();