n = int(input())

dp = [[0.0 for _ in range(7)] for _ in range(n + 1)]
dp[1][1] = 1.0
for i in range(1, n):
  for j in range(1, 7):
    if j < 6:
      dp[i + 1][j + 1] += dp[i][j] * (1 - j / 6)
    dp[i + 1][j] += dp[i][j] * (j / 6)

print(dp[-1][6])