def oushu(x):
s = 0
k = 0
for i in range(x//2):
s += 1/(k + 2)
k += 2
return s
def jishu(x):
s = 0
for i in range(1,x+1):
if i%2 != 0:
s += 1/i
else:
continue
return s
def panduan(x):
if x % 2 == 0:
return oushu(x)
else:
return jishu(x)
def main():
try:
x = eval(input("请输入一个整数："))
print('{:.2f}'.format(panduan(x)))
except:
print('输入格式错误!')
main()
