读取txt文件中的负数？？？

U.txt中的数据
-721.687179 -815.804502 -811.202694 -789.820228 -819.852144 -892.327928 -855.463031 -896.633812 -883.067909 -854.481898 -827.922019 -881.006647 -834.705544 -823.172092 -806.361069 -817.773490 -838.073045 -839.921275 -928.714609 -837.331740 -816.831521 -721.687179 -815.804502 -811.202694