Exchange slider with text field for route length

Hi there,

I love this app and basically use it for all routing and traveling I do. It successfully managed to plan a trip from western Germany to Sweden with ease, so first and foremost: Thank you for the effort you put into this!

I'd have one small suggestion: I sometime use the app to plan long circular rides e.g. for 24h racing. Currently, the way to adjust the length of the suggested route is controlled via a slider and I think it would be more precise to just have a field for text input. By that, the current maximum of ~350 km could be increase if I want to plan a circular multi day route, which I believe is currently not possible. 

Cheers,
Dominik