Click Button on Web Page - No element ID, tagname

[xolo]

I am trying to click a submit button on a web page which doesnt have any element ID or tag name. All I have is input type="submit" class="btn_a" name="update" value="Create" title="Create"
How do I click this button?

[Jack the Tipper]

I am trying to click a submit button on a web page which doesnt have any element ID or tag name. All I have is input type="submit" class="btn_a" name="update" value="Create" title="Create"
How do I click this button?

use getElementsByClassName("btn_a")[0].click()