dp = [0] * 101
dp[0], dp[1] = (1 << 202), (3 << 198)
for i in range(2, 101):
    dp[i] = dp[i - 1] * 19 // 16 - dp[i - 2] * 12 // 64
n = int(input())
for i in range(100 - n):
    dp[n] /= 4
print("{:.100f}".format(dp[n]))