Maximum Staircase Height

Given an integer B which represents the number of blocks available, construct the highest possible staircase. In the staircase, the first row requires 1 block, the second row requires 2 blocks, the third row requires 3 blocks, and so on. The problem is to determine the maximum height h such that the sum of the first h natural numbers, (\frac{h(h+1)}{2}), does not exceed B.

For example, if B = 6, the staircase can have at most 3 rows (since 1 + 2 + 3 = 6).

inputFormat

The input consists of a single integer B which denotes the number of blocks available.

outputFormat

Output a single integer which is the maximum height of the staircase that can be built with B blocks.## sample

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