zeta_table = {
    3: 1.2020569032,
    4: 1.0823232337,
    5: 1.0369277551,
    6: 1.0173430619,
    7: 1.0083492774,
    8: 1.0040773562,
    9: 1.0020083928,
    10: 1.0009945751,
    11: 1.0004941886,
    12: 1.0002460866,
    13: 1.0001227133,
    14: 1.0000612482,
    15: 1.0000305882,
    16: 1.0000152823,
    17: 1.0000076372,
    18: 1.0000038173,
    19: 1.0000019082,
    20: 1.0000009540,
}

N = int(input())
s = N + 2

if s in zeta_table:
    print("{0:.9f}".format(zeta_table[s]))
else:
    print("1.000000000")