Unfortunately, the software doesn't allow you to use the Cyrillic characters, but you can try Google Input Tools. Navigate to the official web page, check the box next to Russian and/or Serbian and then press the blue Download button. Save the file to your computer and install it following the on-screen steps. After that, navigate to Control Panel > Clock, Language, and Region > Religion and Language, open the Keyboards and Languages tab and then press Change keyboards. Press Language bar, check the box next to Docked in the taskbar, click Apply and then OK. Next, you need to press the EN button from System Tray and to select RU or SR:
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