#include<iostream>
#include<string>
#include<queue>
#include<vector>
#include<cassert>
#include<random>
#include<set>
#include<map>
#include<cassert>
#include<unordered_map>
#include<bitset>
#include<numeric>
#include<algorithm>
using namespace std;
typedef long long ll;
const int inf=1<<30;
const ll INF=1LL<<62;
typedef pair<int,ll> P;
typedef pair<int,P> PP; 
const ll MOD=998244353;
const int MAXN=3*1000000;


vector<pair<ll,ll>> calc_gcd(ll n){
    vector<ll> f;
    for(ll v=1;v*v<=n;v++){
        if(n%v==0){
            f.push_back(v);
            if(n/v!=v){
                f.push_back(n/v);
            }
        }
    }
    sort(f.rbegin(),f.rend());
    map<ll,ll> cnt;
    vector<pair<ll,ll>> ans;

    for(ll v:f){
        cnt[v]=n/v;//1~nまでの数でvの倍数の個数
        for(ll t=2*v;t<=n;t+=v){
            //約数の倍数は除外
            cnt[v]-=cnt[t];
            
        }
        ans.emplace_back(v,cnt[v]);
    }
    return ans;
}

int main(){
    ll N;
    cin>>N;
    vector<ll> factor;
    for(ll d=1;d*d<=N;d++){
        if(N%d==0){
            factor.push_back(d);
            if(N/d!=d){
                factor.push_back(N/d);
            }
        }
    }

    sort(factor.begin(),factor.end());

    vector<double> dp(N+1,0);

    for(ll v:factor){
        if(v==1) continue;

        auto array=calc_gcd(v);
        double d=0;
        for(auto [p,cnt]:array){
            if(p==v) continue;
            d+=(1.0*cnt/v)*dp[p];
        }

        d+=1;
        d=(d*v)/(v-1);
        dp[v]=d;
    }

    printf("%.10f\n",dp[N]);

}