You have `n` coins and you want to build a staircase with these coins. The staircase consists of `k` rows where the `ith` row has exactly `i` coins. The last row of the staircase may be incomplete.

Given the integer `n`, return the number of complete rows of the staircase you will build.

Example 1:

    Input: n = 5
    Output: 2
    Explanation: Because the 3rd row is incomplete, we return 2.

Example 2:

    Input: n = 8
    Output: 3
    Explanation: Because the 4th row is incomplete, we return 3.

Constraints:

- `1 <= n <= 231 - 1`