title: Sum for multiple keys
body: <p>I need to calculate population of my chosen cities. What formula will do that? I want my formula to be dynamic so that if I add more cities to my chosen cities it should add value(population) to the sum.</p>
  <p><a href="https://i.stack.imgur.com/TMe6a.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/TMe6a.png" alt="enter image description here" /></a></p>