//
// Created by HakuroKawashiro on 2024/8/2.
//
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <vector>
#include <map>
#define ll long long
#define db double
using namespace std;
int main() {
    ll n;
    scanf("%lld",&n);
    vector<ll> dival;
    dival.push_back(n);
    for (ll i = 2;i * i <= n;i++) {
        if (n % i == 0) {
            dival.push_back(i);
            if (i * i != n) {
                dival.push_back(n / i);
            }
        }
    }
    sort(dival.begin(), dival.end());
    ll top = dival.size();
    map<ll,db> dp;
    map<ll,ll> val;
    for (ll x : dival) {
        ll res = x - 1;
        db pro_val = x * 1.0 / res;
        db real_val = 0.0;
        for (ll y : dival) {
            if (y >= x) {
                break;
            }
            if (x % y == 0) {
                res -= val[x / y];
                db sub_val = val[x / y] * 1.0 / (x - 1);
                real_val += sub_val * dp[y];
            }
        }
        val[x] = res;
        real_val += pro_val;
        dp[x] = real_val;
    }
    printf("%.12lf\n",dp[n]);
    return 0;
}