#include <bits/stdc++.h>
using namespace std;
int x[100010], y[100010];
bool bin(long double radius, int n) {
  vector<pair<long double, long double> > v;
  int i;
  for (i = 0; i < n; i++) {
    long double t = 2 * radius - y[i];
    if (t < 0) return false;
    t = sqrt(y[i]) * sqrt(t);
    v.push_back(make_pair(x[i] - t, x[i] + t));
  }
  long double s = -1e20, e = 1e20;
  for (i = 0; i < n; i++) {
    s = max(s, v[i].first);
    e = min(e, v[i].second);
  }
  if (s > e) return false;
  return true;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int n, i, j;
  cin >> n;
  bool b1 = false, b2 = false;
  for (i = 0; i < n; i++) {
    cin >> x[i] >> y[i];
    if (y[i] > 0)
      b1 = true;
    else if (y[i] < 0)
      b2 = true;
  }
  if (b1 & b2) {
    cout << "-1";
    exit(0);
  }
  for (i = 0; i < n; i++) {
    y[i] = abs(y[i]);
  }
  long double l = 0.1, h = 1e16, mid, ans = 1e18;
  for (i = 0; i < 150; i++) {
    mid = (h + l) / 2;
    if (bin(mid, n)) {
      ans = min(ans, mid);
      h = mid;
    } else {
      l = mid;
    }
  }
  cout << fixed << setprecision(9) << ans;
  return 0;
}
