#include <cstdio>
#include <cmath>

double thirdRoot(int q)
{
    if (q == 1) {
        return 1.;
    }

    double xn = q / 2;
    double xn2 = xn;
    double limit = q * 0.00001;
    while (true) {
        xn2 = xn - (xn*xn*xn - q) / (3*xn*xn);
        if (fabs(xn2*xn2*xn2 - q) < limit) {
            break;
        }
        xn = xn2;
    }

    return xn2;
}

int main()
{
    int q;
    while (true) {
        scanf("%d", &q);
        if (q < 0) {
            break;
        }
        printf("%6lf\n", thirdRoot(q));
    }

    return 0;
}
