#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++){
        vector<int> cnt(i + 1);
        cnt[i] = n / divs[i];
        const int r = n - cnt[i];
        dp[i] += double(n) / r;
        for(int j = i - 1; j >= 0; j--){
            cnt[j] = n / divs[j];
            for(int k = j + 1; k <= i; k++){
                if(divs[k] % divs[j] == 0) cnt[j] -= cnt[k];
            }
            dp[i] += dp[j] / r;
        }
    }
    cout << fixed << setprecision(15) << dp.back() << '\n';
}