#include <stdio.h>
double newtonMethod(int n);
double task(double origin, double d, int n);
int main(int argc, char* argv[]) {
int n;
scanf("%d", &n);
double root = newtonMethod(n);
printf("%lf\n", root);
return 0;
}
double newtonMethod(int n) {
int guess = 1;
int dd = guess * guess;
while (dd < n) {
guess++;
dd = guess * guess;
}
return task((double)n, (double)--guess, 1);
}
double task(double origin, double d, int n) {
double next = d / 2 + origin / (2 * d);
if (n == 100) {
return next;
} else {
return task(origin, next, n + 1);
}
}