Fixed example (#1)

examples/ustack_in_using.md

@@ -7,17 +7,25 @@ pip install ufpy
 
 ## Examples
 To create stack, use UStack class.
+```python
 stack = UStack()
+```
 To add an element to the stack, use UStack.append([<element1>, <elementN, ...])
+```python
 stack.append(1, 2, 3, 4, 5)
+```
 To get the top element, use UStack.top()
+```python
 print(stack.top())
 # 5
+```
 To get and remove the top element of the stack, use UStack.pop()
+```python
 print(stack.pop())
 # 5
 print(stack.top())
 # 4
+```
 ## All methods
 | Name    | Args    |
 | ------- | ------- |