#include<bits/stdc++.h>
using namespace std;
const double pos = 1e-5;
int main(){
    int a; // 巴比伦算法求根号n
    cin >> a;
    double g = 1.0; 
    while(abs((a - g * g) / (2 * g)) > pos){ // 判断有其数学含义
        g = (g + a / g) * 0.5;
    }
    cout << g << "\n";
    return 0;
}