# -*- coding: utf-8 -*-
"""
No.80 四角形を描こう
https://yukicoder.me/problems/no/80

"""
import sys
from sys import stdin
input = stdin.readline


def solve(D):
    if D < 4:
        return 0

    h = 1
    w = 1
    for i in range(2, (10000//4)+1):
        if i * 4 <= D:
            h = i
            w = i
        else:
            break

    remaining = D - (h * 2) - (w * 2)
    if remaining >= 2:
        w += 1
    return h * w


def main(args):
    D = int(input())
    ans = solve(D)
    print(ans)


if __name__ == '__main__':
    main(sys.argv[1:])