#include<bits/stdc++.h>
using namespace std;
using LL = long long;
using ULL = unsigned long long;
#define rep(i,n) for(int i=0; i<(n); i++)

LL GCD(LL a, LL b) { return b ? GCD(b, a % b) : a; }

double F(LL j, LL x) {
	double jb = j, xb = x;
	return jb / (pow(jb, xb) * (jb - 1.));
}

int main() {
	LL x; cin >> x;

	double ans = 0.;

	if (x == 2) {
		ans = 1.;
	}
	else {
		for (LL j = 2; log(j) * x < 30.; j++) {
			ans += F(j, x);
		}
	}

	LL ansi = ans * 1000000;
	cout << ansi << endl;

	return 0;
}