#include <bits/stdc++.h>

#define cout std::cout
#define cin std::cin
#define endl '\n'

using ll = long long;

std::vector<ll> divisor(ll n) {
    std::vector<ll> ret;
    for(ll x = 1; x * x <= n; x++) {
        if(n % x == 0) ret.push_back(x);
    }
    for(ll i = (int)ret.size() - (ret.back() * ret.back() == n); i--; ) {
        ret.push_back(n / ret[i]);
    }
    return ret;
}
std::map<ll, double> memo;
std::map<ll, std::vector<ll>> divs;
void init(ll n) {
    auto d = divisor(n);
    for(int i = 0; i < (int)d.size(); i++) {
        for(int j = 0; j <= i; j++) {
            if(d[i] % d[j] == 0)divs[d[i]].push_back(d[j]);
        }
    }
}
double f(ll n) {
    if(n == 1) return 0;
    if(memo.find(n) != memo.end()) {
        return memo[n];
    }
    auto d = divs[n];
    std::map<ll, ll> mp;
    for(int i = (int)d.size(); i--; ) {
        mp[d[i]] = n / d[i];
        for(int j = 2 * d[i]; j <= n; j += d[i]) {
            if(mp.find(j) != mp.end()) mp[d[i]] -= mp[j];
        }
    }
    double ret = 0;
    for(auto [di, cnt]: mp) {
        if(di != n) ret += (f(di) + 1) * cnt;
    }
    return memo[n] = double(ret + 1)/(n - 1);
}
int main() {
    std::ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n; cin >> n;
    init(n);
    cout << std::setprecision(15) << f(n) << endl;
}