N=int(input())
if N==0:
    goukei=0
    for i in range(100000):
        goukei+=1/(i+1)**2
    print(goukei)
else:
    mul=1
    
    for i in range(N):
        mul*=(i+1)
        
    goukei=0
    for i in range(N):
        goukei+=mul/(i+1)
    
    
    print(goukei/mul/N)