// 求平方根

#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;
    }
    printf("%lf\n",l);
    return 0;
}