# Keyboard character is undefined error

I'm trying to compile a simple ISO-8859-2 document,

\documentclass[twocolumn]{article}

\usepackage[czech]{babel}
\usepackage[latin2]{inputenc}
\usepackage[T1]{fontenc}

\usepackage[paperwidth=18cm, paperheight=13cm]{geometry}

\begin{document}
České vysoké učení technické v Praze
\end{document}


The compilation fails at the "č" letters. It keeps saying

! Package inputenc Error: Keyboard character used is undefined
(inputenc) in inputencoding latin2'.


despite the fact that "č" is a latin2 character.

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There seems to be a conflict between the encoding used in your document and the one of your editor. Both encodings: the one declared in your document using inputenc` and the one used for your editor need to be the same; otherwise errors will appear. Make sure both coincide and the problem will disappear.