ACCRA (AFP) - Ghana’s John Dramani Mahama was sworn in as president on Monday at a ceremony attended by thousands in the capital but boycotted by the opposition, which has challenged the election results. Mahama, who initially became head of state following the death of his predecessor John Atta Mills in July, pledged to build on the west African nation’s economic success in a speech after taking the oath. The writer and Afrobeat music fan from the country’s north who recently published a well-received memoir pledged to improve the country’s infrastructure. “We as a country have inherited a powerful legacy, and we are beneficiaries of a mighty history,” the 54-year-old Mahama told the crowd of average Ghanaians.