#include <bits/stdc++.h>
#include <atcoder/all>
using mint = atcoder::static_modint<998244353>;
//using mint = atcoder::static_modint<1000000007>;
using namespace std;
using namespace atcoder;
using ld = long double;
using ll = long long;
#define mp(a,b) make_pair(a,b)
#define rep(i,s,n) for(int i=s; i<n; i++)
const vector<int> dx{1,0,-1,0},dy{0,1,0,-1};

map<int,ld> memo;

ld dfs(int x){
    if(memo.count(x))return memo[x];
    if(x==1)return 0;
    set<int> S;
    for(int i=1; i*i<=x; i++)if(x%i==0)S.insert(-i),S.insert(-x/i);
    map<int,int> f;
    S.erase(-x);
    f[x]=1;
    ld output=0;
    for(auto y:S){

        y=-y;
        int cnt=x/y;
        for(auto [a,b]:f)if(a%y==0)cnt-=b;
        output+=cnt*dfs(y);
        f[y]=cnt;
    }
    // if(x==4){
    //     for(auto [x,y]:f)cout << x << " " << y << "\n";
    // }
    output+=x;
    output/=x-1;
    memo[x]=output;
    return output;
}
int main(){
    int n;
    cin >> n;
    cout << setprecision(16);
    cout << dfs(n);
}