#include<cstdio>
#include<math.h>
using namespace std;
int main(){
double n;
scanf("%lf",&n);
double l = -abs(n), r = abs(n);
const double e = 1e-7;
while(r - l > e){
double mid = (l + r)/2;
if(mid*mid*mid >= n) r = mid;
else l = mid;
}
printf("%lf\n",l);
return 0;
}