__merge_adaptive
__merge_adaptive(__first, __middle, __last, _Distance(__middle - __first),
__merge_adaptive(__first, __middle, __last, _Distance(__middle - __first),
__merge_adaptive(__first, __first_cut, __new_middle, __len11,
__merge_adaptive(__new_middle, __second_cut, __last, __len1 - __len11,
__merge_adaptive(__first, __first_cut, __new_middle, __len11,
__merge_adaptive(__new_middle, __second_cut, __last, __len1 - __len11,
__merge_adaptive(__first, __middle, __last, __len1, __len2,
__merge_adaptive(__first, __middle, __last, __len1, __len2,