Runners in underwear participate in Cupid's Undie Run, a charity event to raise money for neurofibromatosis (NF) research, in Chicago, the United States, on Feb. 16, 2019. (Xinhua/Wang Ping)

Runners in underwear participate in Cupid's Undie Run, a charity event to raise money for neurofibromatosis (NF) research, in Chicago, the United States, on Feb. 16, 2019. (Xinhua/Wang Ping)

Runners in underwear participate in Cupid's Undie Run, a charity event to raise money for neurofibromatosis (NF) research, in Chicago, the United States, on Feb. 16, 2019. (Xinhua/Wang Ping)

Runners in underwear participate in Cupid's Undie Run, a charity event to raise money for neurofibromatosis (NF) research, in Chicago, the United States, on Feb. 16, 2019. (Xinhua/Wang Ping)

Runners in underwear participate in Cupid's Undie Run, a charity event to raise money for neurofibromatosis (NF) research, in Chicago, the United States, on Feb. 16, 2019. (Xinhua/Wang Ping)

Runners in underwear participate in Cupid's Undie Run, a charity event to raise money for neurofibromatosis (NF) research, in Chicago, the United States, on Feb. 16, 2019. (Xinhua/Wang Ping)

Runners in underwear participate in Cupid's Undie Run, a charity event to raise money for neurofibromatosis (NF) research, in Chicago, the United States, on Feb. 16, 2019. (Xinhua/Wang Ping)