# [Solved] 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.

## Question

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`

## Python Solution

```class Solution:
def arrangeCoins(self, n: int) -> int:
if n==1:
return 1
l=0
r=n//2 + 1
while l<=r:
m = l+(r-l)//2
x = (m*(m+1)//2)
if x==n:
return(m)
elif x<n:
l = m+1
else:
r=m-1
return(l-1)```