#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); ++i)
 
using namespace std;

vector<int> factorize(int n) {
    vector<int> res;
    for (int i = 2; i*i <= n; ++i) {
        if (n%i != 0) continue;
        res.push_back(i);
        while (n%i == 0) n /= i;
    }
    if (n != 1) res.push_back(n);
    return res;
}

int main() {
    int n;
    cin >> n;
    
    auto fs = factorize(n);
    int m = fs.size();
    int m2 = 1<<m;
    
    double ans = 1;
    for (int s = 1; s < m2; ++s) {
        int d = 1;
        rep(i, m) if (s>>i&1) d *= fs[i];
        int cnt = n/d;
        double now = cnt*1./(n-cnt);
        if (__builtin_parity(s)) ans += now;
        else ans -= now;
    }
    
    printf("%.10f\n", ans);
    
    return 0;
}