This example shows a React application that renders three headings, each displaying the numbers 1, 2, and 3 from an array. The code uses React 18.2.0 with the UMD builds of `react` and `react-dom`, and the `createRoot` API from `react-dom` to mount the app. The `App` component maps over the array to generate the heading elements, which are styled with a large font size via CSS in `index.html`.