Effect: Given $ $ a n-tuple $ (val_i, mask_i) $ guaranteed $ \ sum val_i $ $ $ 0 is not.
Selecting a required number of $ S $, for each tuple $ (val_i, mask_i) $, if $ s \ & mask_i $ odd number of bits of $ 1 $, then changed to $ val_i $ $ -val_i $. the initial and final required and opposite sign.