题目

                                   C On a BA flight from Johannesburg, a middle-aged, well-off white South African Lady has found herself sitting next to a black man. She called a stewardess (女乘务员) over to complain about her seating. “What seems to be the problem, Madam?” asked the stewardess. “Can’t you see?” she said, “You’ve sat me next to a kafir（异教徒）. I can’t possibly sit next to this disgusting man. Find me another seat!” “Please calm down, Madam,” the stewardess replied. “The flight is very full today, but I’已知|a-2007|+=a，则a-20072的值是    ．