Open Doors Problem

In this problem, you are given an integer k representing the number of door operations. Initially, all doors are closed. For each door numbered from 1 to k, a toggle operation is performed: if the door is closed, it gets opened, and if it is open, it gets closed. However, only the doors at positions which are perfect squares remain open at the end because they are toggled an odd number of times. Mathematically, the answer is given by: $$\lfloor \sqrt{k} \rfloor$$, where $$\lfloor x \rfloor$$ denotes the floor function.

inputFormat

Input is given via standard input and consists of a single integer k, which represents the total number of door operations.

outputFormat

Output a single integer to standard output representing the number of doors that remain open.## sample

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