import itertools
N = int(input())

if N == 1:
    print(0)
    exit(0)

E = []
O = []
A = []
if N%2 == 0:
    for k in range(1,N//2):
        if k%2 == 1:
            E.append([k,N-k])
        else:
            O.append([N-k,k])
    O = O[::-1]
    for e in E:
        A += e
    A += [N//2]
    for o in O:
        A += o
    A.append(N)
else:
    for k in range(1,N+1):
        if k%2 == 1:
            A.append(k)
        else:
            A.append(N-k+1)

ans = 0
for k in range(1,N):
    ans += A[k-1]*A[k] + A[k]-A[k-1]
ans += A[-1]*A[0] + A[0]-A[-1]
print(ans)