from collections import deque
N = int(input())
if N == 1:
    print(0)
    exit()
D = deque(range(2,N+1))
now = 1
ans = 0
A = [[1],[1]]
st = 0
while D:
    for i in range(2):
        if D:
            if st == 0:
                A[i].append(D.pop())
            else:
                A[i].append(D.popleft())
    st ^= 1
A[0] += A[1][::-1]
ans = 0
for i in range(N):
    ans += A[0][i]*A[0][i+1]
print(ans)