#include <iostream>

using namespace std;

int main()
{
    double x;
    cin >> x;

    double l = 0, r = x + 1;
    while (r - l > 1e-8)
    {
        double mid = (l + r);
        if (mid * mid >= x) r = mid;
        else l = mid;
    }

    printf("%lf\n", l);

    return 0;
}