def main():
    n = int(input())
    a = [0,0]
    for i in range(1, n+1):
        a[0] += 1
        a[1] = a[1] + 1 if i % 2 != 0 else a[1]
    print(a[1] / a[0])

if __name__ == '__main__':
    main() def main():
    n = int(input())
    a = [0,0]
    for i in range(1, n+1):
        a[0] += 1
        a[1] = a[1] + 1 if i % 2 != 0 else a[1]
    print(a[1] / a[0]) main n = int(input()) n int(input()) int input() input a = [0,0] a [0,0] 0 0 for i in range(1, n+1):
        a[0] += 1
        a[1] = a[1] + 1 if i % 2 != 0 else a[1]
     i range(1, n+1) range 1 n+1 n 1 a[0] += 1 a[0] a 0 1 a[1] = a[1] + 1 if i % 2 != 0 else a[1] a[1] a 1 a[1] + 1 if i % 2 != 0 else a[1] i % 2 != 0 i % 2 i 2 0 a[1] + 1 a[1] a 1 1 a[1] a 1 print(a[1] / a[0]) print a[1] / a[0] a[1] a 1 a[0] a 0 if __name__ == '__main__':
    main() __name__ == '__main__' __name__ '__main__' main() main def main():
    n = int(input())
    a = [0,0]
    for i in range(1, n+1):
        a[0] += 1
        a[1] = a[1] + 1 if i % 2 != 0 else a[1]
    print(a[1] / a[0]) def main():
    n = int(input())
    a = [0,0]
    for i in range(1, n+1):
        a[0] += 1
        a[1] = a[1] + 1 if i % 2 != 0 else a[1]
    print(a[1] / a[0]) main
def main():
    n = int(input())
    a = [0,0]
    for i in range(1, n+1):
        a[0] += 1
        a[1] = a[1] + 1 if i % 2 != 0 else a[1]
    print(a[1] / a[0])

if __name__ == '__main__':
    main()