1x3x5x7x ……x99=1x2x3x4x5……x99x100÷（2x4x6x8x……98x100）
=1x2x3x4x5……x99x100÷(2^50x(1x2x3x4x5……x49x50))
=100!÷50!÷2^50
=3.0685187562549660372027304595295e+93÷2^50
=2.7253921397507295029807132454009e+78
1x3x5x7x ……x99=1x2x3x4x5……x99x100÷（2x4x6x8x……98x100）
=1x2x3x4x5……x99x100÷(2^50x(1x2x3x4x5……x49x50))
=100!÷50!÷2^50
=3.0685187562549660372027304595295e+93÷2^50
=2.7253921397507295029807132454009e+78
