/**************************************
*   正数开方                          *   
*                                     * 
**************************************/
# include <iostream>
using namespace std;
double St (double X){
    float x[10]={0},k;
    int i;
    while (k*k>=X){
        i=0;
        k=i;
        i++;
    };
    x[0]=k;
    for(i=0;i<10;i++){
    x[i+1]= (x[i]+X/x[i])/2.0;
    };
    return x[i+1];
}
int main (){
    double m;
    cin>>m;
    cout<<St(m)<<endl;
    return 0;
}