The UK's largest spy agency GCHQ has sent out its annual Christmas card complete with a brainteaser.
원문출처 : https://www.cnn.com/2020/12/18/uk/gchq-christmas-card-puzzle-scli-intl-gbr/index.html
원문출처 : https://www.cnn.com/2020/12/18/uk/gchq-christmas-card-puzzle-scli-intl-gbr/index.html