from functools import cache
@cache
def f(n):
    if n==1: return 0
    s = set(); d = {}; x = 0
    for i in range(1,int(n**0.5)+1):
        if n%i==0: s |= {i,n//i}
    s.remove(n); s = sorted(s); m = len(s)
    for i in range(m-1,-1,-1):
        d[s[i]] = (n-1)//s[i]
        for j in range(i+1,m):
            if s[j]%s[i]==0: d[s[i]] -= d[s[j]]
        x += d[s[i]]*f(s[i])
    return (x/n+1)*n/(n-1)
print(f(int(input())))