N = int(input())
import sys
if N == 1:
    print(0)
    exit()
    
from collections import deque
l = list(range(2,N+1))
q = deque(l)
p = deque()
p.append(1)
count = 0
while q:
    if count == 0:
        t = q.pop()
        p.append(t)
    elif count == 1:
        t = q.pop()
        p.appendleft(t)
    elif count == 2:
        t = q.popleft()
        p.append(t)
    else:
        t = q.popleft()
        p.appendleft(t)
    count = (count + 1) % 4
ans = p[0] * p[-1]
for i in range(len(p)-1):
    ans += p[0] * p[1]
    p.popleft()
print(ans)