<em> consider a mountain whose summit is 5,000 feet (1,500 m) in elevation, but somewhere on the way up, the trail goes back down 250 feet (76 m). ... </em>
<em>If one hikes over five hills of 100 vertical feet each, the cumulative elevation gain is 5 × (100 feet (30 m)) = 500 feet (150 m).</em>
