#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n;
    cin >> n;
    vector<int> divs;
    for(int i = 1; i * i <= n; i++){
        if(n % i == 0){
            divs.emplace_back(i);
            if(i * i != n) divs.emplace_back(n / i);
        }
    }
    sort(divs.begin(), divs.end());
    const int m = divs.size();
    vector<double> dp(m);
    for(int i = 1; i < m; i++){
        int r = n - n / divs[i], cnt = 0;
        double add = double(n) / r;
        for(int j = 0; j < m; j++){
            int g = gcd(divs[i], divs[j]);
            if(g == divs[i]) continue;
            cnt++;
            int p = lower_bound(divs.begin(), divs.end(), g) - divs.begin();
            dp[i] += (dp[p] + add) / r;
        }
        dp[i] += (dp[0] + add) / r * (r - cnt);
    }
    cout << fixed << setprecision(15) << dp.back() << '\n';
}