You have `n` coins and you want to build a staircase with them. The staircase consists of `k` rows where the `i`-th 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:Rows of 1 and 2 coins are complete (3 coins used); the third row only gets 2 of the 3 coins it needs.
Example 2
Input:n = 8
Output:3
Explanation:Rows 1, 2, 3 use 6 coins; the fourth row gets only 2 of 4.