#include <bits/stdc++.h>
using namespace std;

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
 
    int C; cin >> C;
    __int128_t v = 0,c = C;
    c *= 1'000'000'000'000'000LL;
    while(true){
        v++;
        __int128_t now = v*v*v*v*v+v*1'000'000'000'000LL-c;
        if(now > 0){
            v--;
            long long answer = v;
            cout << answer/1000 << ".",answer %= 1000;
            cout << answer/100,answer %= 100;
            cout << answer/10,answer %= 10;
            cout << answer/1,answer %= 1;
            cout << endl;
            break;
        }
    }
}