# [Husk], 14 bytes

    ◄§-▼▲fo=▲¹ΣΠR3

[Try it online!][TIO-kxq4u8v3]


### Explanation

    ◄§-▼▲fo=▲¹ΣΠR3
                R3   repeat input 3 times
               Π     cartesian product
         fo          filter by composed function
           =▲¹Σ      max of input equals sum
    ◄§               min by composed binary function
      -▼▲            max - min


[Husk]: https://github.com/barbuz/Husk
[TIO-kxq4u8v3]: https://tio.run/##yygtzv7//9H0lkPLdR9N2/No2qa0fFsgeWjnucXnFgQZ////P9pQx0jHWMdEx1THTMdcx0LHUsfQIBYA "Husk – Try It Online"