#include <cstdio>
int main() {
double n;
scanf("%lf", &n);
double l = -100, r = 100;
double a;
while (r - l > 1e-8) {
a = (l + r) / 2.0;
if (a * a * a < n) {
l = a;
} else {
r = a;
}
}
printf("%.6lf\n", l);
return 0;
}