Click on a button with no Id using Webdriver

I am trying to click on the OK button in the following html code. Can anyone please help ?

OK
OK


How do i find this element in driver.findElement ?

Thanks,

I pasted the html code for OK button ...

here is the code :

button type="button" class="ui-button ui-widget ui-state-default ui-corner-all ui-button-text-only" role="button" aria-disabled="false"
span class="ui-button-text">OK/button

Use this command

wait.Until((d) => { return d.FindElement(By.XPath("//button[.='Ok']")); });

driver.FindElement(By.XPath("//button[.='Ok']")).Click();