1.0rich700784https://stepik.org/lesson/407776/Stepikhttps://stepik.org/<iframe src="https://stepik.org/lesson/407776/" scrolling="no" frameborder="0" width="700" height="784" allowfullscreen webkitallowfullscreen mozallowfullscreen sandbox="allow-scripts allow-modals allow-forms allow-same-origin allow-popups allow-popups-to-escape-sandbox"></iframe>