# Demo Article

You can see the source of this article to better understand formatting features.

The header is made of line starting with # (hash) symbol. Note that also we need to add a magical ?title comment which defines the title of the resulting HTML page for browser and search engines (see the source of this page - it is in the top).

Text is written in paragraphs, separated with empty lines. Line breaks in paragraphs are regarded as ordinary spaces. If you add a couple of extra spaces in the line end, they will create "hard line-break" in that place.

The code snippets are created of blocks indented with 4 spaces:

#include <stdio.h>
int main() {
printf("Hello, World\n");
}

For long blocks it would be good to add "show/hide" button. It is created by adding small magic span in the end of the preceding paragraph Show/Hide

int phi(int n) {
int result = n;
for(int i = 2; i * i <= n; ++i)
if(n % i == 0) {
while(n % i == 0)
n /= i;
result -= result / i;
}
if(n > 1)
result -= result / n;
return result;
}

### TeX and Markdown references

We use Markdown for source texts and convert them automatically to HTML. Some extra features also could be used.

Formulas could be added thanks to MathJax library. Simply use TeX expressions inside single or double dollar marks $, for example: here is an inline equation:$P \ne NP\$

And here is the formula in the separate block:

$$E = mc^{2}$$