#include<bits/stdc++.h>
using namespace std;
int main(){
    double x;
    cin >> x;
    int l = 0, r = x;
    while(r - l > 1e-6){
        double mid = (l + r) >> 1;
        if(mid * mid >= x) r = mid;
        else l = mid;
    }
    printf("%lf\n",l);
    return 0;
}