N = input()
S = 'a'
# while (True):
#     S += 'ba'
#     if (len(S) == N):
#         break
# pail = [[False] * 50 for i in range(50)]
# for i in range(N):
#     left = i
#     right = i
#     while (left >= 0 and right < N):
#         if (S[left] == S[right]):
#             pail[left][right] = True
#         else:
#             break
#         left -= 1
#         right += 1
#     left = i
#     right = i + 1
#     while (left >= 0 and right < N):
#         if (S[left] == S[right]):
#             pail[left][right] = True
#         else:
#             break
#         left -= 1
#         right += 1
# res = 0
# for i in range(N):
#     for j in range(i, N):
#         if ((j - i) + 1 >= 2 and pail[i][j]):
#             res += 1
# print res
a = N / 2
print a ** 2