#include <bits/stdc++.h>
using namespace std;
typedef signed long long ll;

#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define FORR2(x,y,arr) for(auto& [x,y]:arr)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
template<class T> bool chmax(T &a, const T &b) { if(a<b){a=b;return 1;}return 0;}
template<class T> bool chmin(T &a, const T &b) { if(a>b){a=b;return 1;}return 0;}
//-------------------------------------------------------

int N;
vector<int> V;

map<int,double> M;
double hoge(int v) {
	if(v==1) return 0;
	if(M.count(v)) return M[v];
	int x=lower_bound(ALL(V),v)-V.begin();
	int dp[500]={};
	int i,j,k;
	for(j=x;j>=0;j--) if(v%V[j]==0) {
		dp[j]=v/V[j];
		for(i=j+1;i<=x;i++) if(V[i]%V[j]==0) dp[j]-=dp[i];
	}
	double ret=v/(v-1);
	FOR(i,x) if(dp[i]) ret+=dp[i]*hoge(V[i]);
	return M[v]=ret;
	
}

void solve() {
	int i,j,k,l,r,x,y; string s;
	
	cin>>N;
	for(i=1;i*i<=N;i++) if(N%i==0) {
		V.push_back(i);
		if(i*i!=N) V.push_back(N/i);
	}
	sort(ALL(V));
	
	_P("%.12lf\n",hoge(N));
		
	
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false), cin.tie(0);
	FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	cout.tie(0); solve(); return 0;
}