#IBM/Lotus Notes Formula, 21 bytes

    @Left(a;@Length(a)/2)

Computed field that takes input from an editable field a. Works because Notes rounds up when an odd number is divided by 2. 

Test Cases

[![test case 1][1]][1]

[![test case 2][2]][2]

[![test case 3][3]][3]

[![test case 4][4]][4]


  [1]: https://i.sstatic.net/A9Oq3.png
  [2]: https://i.sstatic.net/15Fxi.png
  [3]: https://i.sstatic.net/MIEZR.png
  [4]: https://i.sstatic.net/4CKqd.png