#include <bits/stdc++.h>
using namespace std;
int n;
pair<double, double> p[100010];
double g(double piv, double x, double y) {
  x = fabs(x - piv);
  y = fabs(y);
  return ((y * y + x * x) / (y * 2));
}
double f(double x) {
  double maxi = -1;
  for (int i = 0; i < n; i++) {
    maxi = max(maxi, g(x, p[i].first, p[i].second));
  }
  return maxi;
}
int main() {
  cin.tie(0);
  ios_base::sync_with_stdio(0);
  bool sp = 0;
  bool sn = 0;
  cin >> n;
  for (int i = 0; i < n; i++) {
    double x, y;
    cin >> x >> y;
    p[i] = make_pair(x, y);
    if (y > 0)
      sp = 1;
    else
      sn = 1;
  }
  if ((sp && sn)) {
    cout << -1 << endl;
    return 0;
  }
  double l = -10000000;
  double r = 10000000;
  double eps = 0.0000001;
  double fl = f(l);
  double fr = f(r);
  while (1) {
    double one = (l * 2 + r) / 3;
    double two = (r * 2 + l) / 3;
    double r1 = f(one);
    double r2 = f(two);
    if (r1 <= r2) {
      r = two;
      fr = r2;
    } else {
      l = one;
      fl = r1;
    }
    if (fl - fr < eps && r - l < eps) break;
  }
  cout << fixed << setprecision(8) << (fl + fr) / 2 << endl;
}
