U.S. President Obama shares a laugh with Danish PM Thorning-Schmidt as his wife, U.S. first lady Michelle looks on during a memorial service for late South African President Nelson Mandela in Johannesburg

U.S. President Barack Obama (C) shares a laugh with Danish Prime Minister Helle Thorning-Schmidt (L) as his wife, U.S. first lady Michelle Obama looks on during a memorial service for late South African President Nelson Mandela at the FNB soccer stadium in Johannesburg December 10, 2013. Picture taken December 10. REUTERS/Kai Pfaffenbach (SOUTH AFRICA – Tags: POLITICS OBITUARY)