Programming skills required by mathematicians?

Hello,

I'm a highschool graduate and I'm going to major in Mathematics this
Fall. I would like to have a foundation in programming so that it
would be useful in my later career as a mathematician with interests
in logic, numerical analysis, formal systems and that sort.

I don't know enough technicalities to seek the right sort of
programming that I should learn now. I wish to hear advice on what
sort of programming skills a pure mathematician would find useful.

Regards.

PS - At the moment, I know only the basics of C++.