#include <bits/stdc++.h>

//const static double	de_PI	= 3.14159265358979323846;
//const static int	de_MOD	= 1000000007;
//const static int	de_MAX	= 999999999;
//const static int	de_MIN = -999999999;

inline void Erase_LeadingZero(std::string &A) {

	if (A.length() <= 18) {
		unsigned long long temp = std::stoull(A);
		A = std::to_string(temp);
	}
	else {
		std::reverse(A.begin(), A.end());
		while (A.back() == '0') { A.pop_back(); }
		std::reverse(A.begin(), A.end());
	}
}

inline std::string Multiply_MultiplePrecision(const std::string &str1, const std::string &str2) {

	std::string A = str1, B = str2;

	unsigned int dp = 0;
	if (A.find('.', 0) != std::string::npos) {
		dp += A.length() - (A.find('.', 0) + 1);
		A.erase(A.begin() + A.find('.', 0));
		Erase_LeadingZero(A);
	}
	if (B.find('.', 0) != std::string::npos) { 
		dp += B.length() - (B.find('.', 0) + 1);
		B.erase(B.begin() + B.find('.', 0));
		Erase_LeadingZero(B);
	}

	int al = A.length(), bl = B.length(), cl = al + bl;
	std::vector<int> a(al), b(bl), c(cl + 1);
	for (int i = 0; i < al; i++) { a[i] = A[al - 1 - i] - '0'; }
	for (int i = 0; i < bl; i++) { b[i] = B[bl - 1 - i] - '0'; }

	for (int i = 0; i < bl; i++) {
		for (int j = 0; j < al; j++) { c[i + j] += b[i] * a[j]; }
	}

	for (int i = 0; i < cl; i++) {
		c[i + 1] += c[i] / 10;
		c[i] = c[i] % 10;
	}

	std::string ans(cl, 0);
	for (int i = 0; i < cl; i++) { ans[cl - i - 1] = static_cast<char>(c[i]) + '0'; }
	Erase_LeadingZero(ans);

	if (dp != 0) {
		if (dp >= ans.length()) {
			std::string temp = ans;
			ans = "0.";
			for (unsigned int i = 0; i < dp - temp.length(); i++) { ans += "0"; }
			ans += temp;
		}
		else {
			ans.insert(ans.begin() + ans.length() - dp, '.');
		}
	}

	return ans;
}

int main(void) {

	//std::ifstream in("123.txt");	std::cin.rdbuf(in.rdbuf());
	std::string D = "0.1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495969798991";
	std::string N;
	std::cin >> N;

	std::cout << Multiply_MultiplePrecision(D, N) << std::endl;
}