#include <bits/stdc++.h>
using namespace std;
#define ll long long
int main() {
    long double x, low, mid, high;
    cin >> x;
    low = 1;
    high = x;
    mid = low + (high - low)/2;
    int p = 2000000;
    while(p--) {
        if(mid * mid > x) {
            high = mid;
            mid = low + (high - low)/2;
        }
        else{
            low = mid;
            mid = low + (high - low)/2;
        }
        if(low>high) {
            break;
        }
    }
    cout << fixed << setprecision(70) << mid;
}