（1/100-1)x(1/99-1)x(1/98-1)x...x(1/2-1)
.=（1-100/100)x(1-99/99)x(1-98/98)x...x(1-2/2)
=（-99/100)x(-98/99)x(-97/98)x...x(-1/2)
=-（99/100)x(98/99)x(97/98)x...x(1/2)
=-1/100