There is a biker going on a road trip. The road trip consists of `n + 1` points at different altitudes. The biker starts his trip on point `0` with altitude equal `0`.

You are given an integer array `gain` of length `n` where `gain[i]` is the net gain in altitude between points `i`​​​​​​ and `i + 1` for all (`0 <= i < n)`. Return the highest altitude of a point.

Example 1:

    Input: gain = [-5,1,5,0,-7]
    Output: 1
    Explanation: The altitudes are [0,-5,-4,1,1,-6]. The highest is 1.

Example 2:

    Input: gain = [-4,-3,-2,-1,4,3,2]
    Output: 0
    Explanation: The altitudes are [0,-4,-7,-9,-10,-6,-3,-1]. The highest is 0.

Constraints:

- `n == gain.length`
- `1 <= n <= 100`
- `-100 <= gain[i] <= 100`