#include<bits/stdc++.h>
using namespace std;

int gcd(int a, int b) {
    while (b != 0) {
        int temp = b;
        b = a % b;
        a = temp;
    }
    return a;
}

double fill_dp(int N,vector<double> dp){ // N番目をうめる
	if(dp[N] >= 0){
		return dp[N];
	}
	if(N == 1){
		dp[1] = 0.0;
		return dp[1];
	}
	double sum_e = 0.0;
	for(int k=1;k<N;k++){
		sum_e += fill_dp(gcd(N,k),dp);
	}
	dp[N] = (sum_e+(double)N)/(double)(N-1);
}


int main(){
	int N;
	cin >> N;
	vector<double> dp(N+1,-1);
	cout << fill_dp(N,dp) << endl;
}