1*1/3+3*1/5+5*1/7+.+99*1/101
=1/3+3/5+5/7+.+99/101
=(1-2/3)+(1-2/5)+(1-2/7)+.+(1-2/101)
=1*50-2(1/3+1/5+1/7+.1/101)
=