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

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int N; cin >> N;
    vector<vector<int>> Ds(N+1);
    for(int i=1; i<=N; i++) for(int k=i; k<=N; k+=i) Ds.at(k).push_back(i);
    vector<double> P(N+1);
    double answer = 0;
    P.at(N) = 1;
    for(int i=N; i>1; i--) if(P.at(i) > 1e-10){
        int n = Ds.at(i).size();
        vector<int> C(n);
        for(int k=n-1; k>=0; k--){
            int d = Ds.at(i).at(k);
            int now = N/d;
            for(int l=k+1; l<n; l++) if(Ds.at(i).at(l)%d == 0) now -= C.at(l);
            C.at(k) = now;
        }
        double multi = N/(0.0+N-C.at(n-1));
        answer += multi*P.at(i);
        for(int k=0; k<n-1; k++){
            int d = Ds.at(i).at(k);
            P.at(d) += P.at(i)*C.at(k)/(N-C.at(n-1));
        }
    }
    cout << fixed << setprecision(20) << answer << endl;

}