A sandstorm sweeps across as competitors take part in the 33rd edition of Marathon des Sables, in the Sahara desert, near Merzouga, southern Morocco, Wednesday, April 14, 2018. The 33rd edition of the annual race, considered to be one of the most demanding ultramarathons in the world, finished Saturday after six grueling days and about 250 kilometers (150 miles). (AP Photo/Mosa'ab Elshamy)