import collections
N = int(input())
if N == 1:
    print(0)
    exit()
ls1 = [1]
ls2 = [1]
d = collections.deque([i+2 for i in range(N-1)])
for i in range((N-1)//2):
    if i % 2 == 0:
        ls1.append(d.pop())
        ls2.append(d.pop())
    else:
        ls1.append(d.popleft())
        ls2.append(d.popleft())
if N % 2 == 0:
    ls1.append(d.pop())
ls2.reverse()
ls = ls1+ls2
ans = 0
for i in range(N):
    ans += ls[i]*ls[i+1]
print(ans)