#ifndef DEBUG
#pragma GCC target("avx2")
#pragma GCC optimize("Ofast,unroll-loops")
#endif
#include <bits/stdc++.h>
#include <atcoder/all>
#define rep(i, n) for (int i = 0; i < n; i++)
#define ALL(a) a.begin(), a.end()
#define vc vector
#define ll long long
using namespace std;
using namespace atcoder;
void solve()
{
	int n;
	cin >> n;
	if (n > 0)
		cout << 0 << '\n';
	else if (n < 0)
	{
		n *= -1;
		vector<double> a(n + 1);
		a[0] = 0.1;
		a[1] = -0.01;
		for (int i = 2; i <= n; i++)
			a[i] = -(a[i - 1] + a[i - 2]) / 10;
		cout << a[n] << '\n';
	}
	else
		cout << 0.1 << '\n';
}
int main()
{
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	cout << fixed << setprecision(40);
	solve();
	return 0;
}