import java.util.Scanner;

public class Sqrt {

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        double num = sc.nextInt();
        sc.close();

        boolean flag = true;
        double left = 0;
        double right = 1e10;
        double mid = 0;
        double root = 0;

        while (flag) {
            mid = (left + right) / 2;
            if (mid * mid - num < 0.00001) {
                flag = false;
                root = mid;
            } else {
                if (mid * mid > num)
                    right = mid;
                else
                    left = mid;
            }
        }
        System.out.println(root);

    }
}