Iivo Niskanen of Finland changes his skis during men's 50km mass start classic of cross-country skiing at the 2018 PyeongChang Winter Olympic Games at Alpensia Cross-Country Skiing Centre, PyeongChang, South Korea, Feb. 24, 2018. Iivo Niskanen won the gold medal in a time of 2:08:22.1. (Xinhua/Fei Maohua)