WASHINGTON, DC - AUGUST 03: A participant in the Presidential Summit of the Mandela Washington Fellowship for Young African Leaders poses with a Nigerian flang before a town hall event at the Omni Shoreham Hotel August 3, 2016 in Washington, DC. As part of Obama's Young African Leaders Initiative, the summit brought together 500 leaders, ages 25-35, from across Africa to the U.S. for 6 weeks of leadership training and mentoring at twenty universities and colleges to 'spur growth and prosperity, strengthen democratic governance, and enhance peace and security across Africa.' (Photo by Chip Somodevilla/Getty Images)

U.S. President Barack Obama answers a question as he and Singapore's Prime Minister Lee Hsien Loong hold a joint news conference at the White House in Washington, U.S. August 2, 2016. REUTERS/Jonathan Ernst

U.S. President Barack Obama and first lady Michelle Obama host a state dinner for Singapore Prime Minister Lee Hsien Loong and his wife Mrs. Lee Hsien Loong to the White House in Washington U.S., August 2, 2016. REUTERS/Mary F. Calvert

WASHINGTON, DC - AUGUST 03: Participants in the Presidential Summit of the Mandela Washington Fellowship for Young African Leaders pose for photographs before a town hall event at the Omni Shoreham Hotel August 3, 2016 in Washington, DC. As part of Obama's Young African Leaders Initiative, the summit brought together 500 leaders, ages 25-35, from across Africa to the U.S. for 6 weeks of leadership training and mentoring at twenty universities and colleges to 'spur growth and prosperity, strengthen democratic governance, and enhance peace and security across Africa.' (Photo by Chip Somodevilla/Getty Images)

WASHINGTON, DC - AUGUST 03: Participants in the Presidential Summit of the Mandela Washington Fellowship for Young African Leaders use a variety of mobile devices, including tablets and phones, before a town hall event at the Omni Shoreham Hotel August 3, 2016 in Washington, DC. As part of Obama's Young African Leaders Initiative, the summit brought together 500 leaders, ages 25-35, from across Africa to the U.S. for 6 weeks of leadership training and mentoring at twenty universities and colleges to 'spur growth and prosperity, strengthen democratic governance, and enhance peace and security across Africa.' (Photo by Chip Somodevilla/Getty Images)

WASHINGTON, DC - AUGUST 03: Participants in the Presidential Summit of the Mandela Washington Fellowship for Young African Leaders make photographs before a town hall event at the Omni Shoreham Hotel August 3, 2016 in Washington, DC. As part of Obama's Young African Leaders Initiative, the summit brought together 500 leaders, ages 25-35, from across Africa to the U.S. for 6 weeks of leadership training and mentoring at twenty universities and colleges to 'spur growth and prosperity, strengthen democratic governance, and enhance peace and security across Africa.' (Photo by Chip Somodevilla/Getty Images)

WASHINGTON, DC - AUGUST 03: Participants in the Presidential Summit of the Mandela Washington Fellowship for Young African Leaders use a variety of mobile devices, including tablets and phones, before a town hall event at the Omni Shoreham Hotel August 3, 2016 in Washington, DC. As part of Obama's Young African Leaders Initiative, the summit brought together 500 leaders, ages 25-35, from across Africa to the U.S. for 6 weeks of leadership training and mentoring at twenty universities and colleges to 'spur growth and prosperity, strengthen democratic governance, and enhance peace and security across Africa.' (Photo by Chip Somodevilla/Getty Images)

WASHINGTON, DC - AUGUST 03: Participants in the Presidential Summit of the Mandela Washington Fellowship for Young African Leaders use a variety of mobile devices, including tablets and phones, before a town hall event at the Omni Shoreham Hotel August 3, 2016 in Washington, DC. As part of Obama's Young African Leaders Initiative, the summit brought together 500 leaders, ages 25-35, from across Africa to the U.S. for 6 weeks of leadership training and mentoring at twenty universities and colleges to 'spur growth and prosperity, strengthen democratic governance, and enhance peace and security across Africa.' (Photo by Chip Somodevilla/Getty Images)