#include <iostream>
#include <cstdint>
using namespace std;

int main() 
{
	int32_t in;
	cin >> in;
	const bool negative = in < 0;
	const uint32_t a    = negative ? - in : in;
	const uint32_t half = a >> 1;
	const bool odd      = a & 0x1;
	cout << (negative ? '-':' ') << half << '.' << (odd ? '5' : '0') << endl;
	return 0;
}