class Solution:
    def arrangeCoins(self, n: int) -> int:
        l, r = 1, n
        res = 0
        while l <=r:
            mid = (l+r)//2
            coins = (mid /2) * (mid+1)
            if coins > n:
                r = mid - 1
            else:
                l = mid + 1
                res = max(mid, res)
        return res