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

long long intpow(long long a, long long b){ 
    long long ans = 1; 
    while(b){ 
        if(b & 1) ans *= a; 
        a *= a; 
        b >>= 1; 
    } 
    return ans;
}

int main(){
    ll c;
    cin >> c;
    __int128 r = intpow(1000, 5), r2 = intpow(1000, 4);
    ll ans = 0;
    for(ll x = 0; x <= 100000; x++){
        __int128 v = x * x * __int128(x) * x * x + x * r2 - c * r;
        if(v <= 0){
            ans = x;
        }
    }
    ll a = ans / 1000;
    ll b = abs(ans) % 1000;
    printf("%lld.%03lld\n", a, b);
}