Random tests in C# expect 0 for start == end cases which is wrong as the answer should be the value of start (already raised as an issue numerous times)

Not a suggestion.

If you can write a brute-force solution (that will pass up to sample test 6) I think you've perfectly understood the descriptions ;-)

(like a certain Haskell solution)

Burst into laughter

Don't use programming tricks to get rid of that division, only mathematics can help you ;-)

As mentioned by lechevalier below, you need to get rid of a certain division ;-)

Don't rely on dirty tricks (like a certain Haskell solution), this is an algorithm kata ;-)

Yes, CW runner servers are using AWS T2 micro IIRC, so only 1 core. :(

This kata presents a rule to know if a number is divisible by 7 or not. You aren't supposed to return if it is or not, you have to follow the rule presented and return the last result of the iteration and the number of steps it took to get that number, there is no contradiction in that.

RTFM! (correctly...)

this last m will be divisible or not by 7