#include <iostream>
#include <boost/multiprecision/cpp_dec_float.hpp>
#include <boost/multiprecision/cpp_int.hpp>
#include <boost/rational.hpp>

using Int = boost::multiprecision::cpp_int;
using Float = boost::multiprecision::cpp_dec_float_100;
using Rational = boost::rational<Int>;

void solve(int k){
	Rational ans = 0;
	for(Int i = 1; i <= k; ++i){
		ans += Rational(1, i);
	}
	ans *= Rational(1, k);
	std::cout << boost::rational_cast<Float>(ans) << std::endl;
}

int main(){
	int k;
	std::cin >> k;
	std::cout << std::setprecision(100);
	if(k == 0) std::cout << boost::math::constants::zeta_two<Float>() << std::endl;
	else solve(k);
}