Arranging Coins

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

SOLUTION:

import math

class Solution:
    def arrangeCoins(self, n: int) -> int:
        k = math.floor((math.sqrt(1 + 8 * n) - 1) / 2)
        return k