## Problem You need to go up **n floors** (from floor 0 to floor n). You may: 1. **Take the elevator first (at most once, only at the start)** for `k` floors, where `0 ≤ k ≤ n`. - For each elevator floor traveled: - You **gain** `e1` energy. - You spend `t1` time. - After riding `k` floors, your energy is `E = k * e1`. 2. **Then climb the remaining `n - k` floors by stairs**. - For each stair floor climbed: - If your current energy before climbing that floor is `E`, the time spent on that floor is: \[ \lceil c / E \rceil \] - After climbing that floor, your energy decreases by `e2`: `E := E - e2` - **Energy must never become negative**, meaning before every stair step you must have `E ≥ e2` (so that after subtracting `e2` you still have `E ≥ 0`). Your task is to choose `k` to **minimize the total travel time**. ## Input Five integers: - `n`: number of floors to go up - `e1`: energy gained per elevator floor - `t1`: time per elevator floor - `e2`: energy spent per stair floor - `c`: constant used in stair time formula ## Output Return the **minimum possible total time** to reach floor `n`. - If it is **impossible** to reach floor `n` for any `k` (i.e., you can’t complete the stair portion without energy going negative), return `-1`. ## Notes / Clarifications - The elevator can be taken **only once and only before any stair climbing**. - Stair time uses the **current energy before** spending `e2` for that floor. - Use 64-bit arithmetic where appropriate.