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Traingle Assembly!

Description

In a large ground, $$N$$ students are instructed to stand in rows such that there are always $$k$$ students in kth row i$.$e $1$ student in row$1,2$ in row$2$ and so on$.$ You need to return the total number of rows that could maintain this pattern.

Constraints

$1<=$N$<=100000$

Examples

Input:

$71$

Output:

$11$

Explanation:

$1,2,3,4,5,6,7,8,9,10,11->66$ students $12$th row will require $12$ students but we have only $5$ left. So$,$ only $11$ rows could maintain the pattern.