# ##################### #
# #                   # #
# #   python3勉強中   # # (ﾟдﾟ)
# #                   # #
# ##################### #
import sys

l = int(input())

if l < 4:
    print(0)
else:
    rslt = 0
    for x in range(int(l/2),0,-1):
        for y in range(int(l/2),0,-1):
            if x*2+y*2 > l : continue
            rslt=max(rslt,x*y)
    print(rslt)