#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++)

int main() {
	cout << fixed << setprecision(10);

	double K; cin >> K;
	K = fmod(K, 2. * acos(-1.));
	double ans = 0.;
	for (int ni = 20; ni >= 1; ni--) {
		double n = ni;
		ans += sin(K * n) / pow(n, n);
	}

	cout << ans << endl;

	return 0;
}