//此时是使用浮点数二分法来求解一个数的平方根。
#include <iostream>
using namespace std;
int main() {
double x;
cin >> x;
double l = 0, r = x;
while (r - l > 1e-8) {
double mid = (l + r) / 2;
if (mid * mid >= x) r = mid;
else l = mid;
}
cout << l << endl;
return 0;
}