The Escalator Race

Three friends race to the top floor: one takes the stairs, one stands on the escalator, one WALKS UP the escalator. 🏃

The stairs are ls steps (climbed at a steps/sec); the escalator is le steps (it moves at e steps/sec — the stander rides at e, the walker moves at a + e). Time = steps ÷ speed, rounded up. Exactly one friend is fastest. Print stairs, stander, or walker.

Example:

Input: ls = 30, a = 3, le = 60, e = 4 Output: walker

Stairs take 30 ÷ 3 = 10s. The stander rides at 4/s, taking 60 ÷ 4 = 15s. The walker moves at 3 + 4 = 7/s, taking ⌈60 ÷ 7⌉ = 9s — the walker is fastest.