【C022032】写一个求和的函数sum，达到下面的效果

// Should equal 15

sum(1, 2, 3, 4, 5);

// Should equal 0

sum(5, null, -5);

// Should equal 10

sum('1.0', false, 1, true, 1, 'A', 1, 'B', 1, 'C', 1, 'D', 1,

  'E', 1, 'F', 1, 'G', 1);

// Should equal 0.3, not 0.30000000000000004

sum(0.1, 0.2);