#include <bits/stdc++.h>
using namespace std;
const int maxn = 100005;
const long double maxx = 2e7;
const long double ubound = maxx * maxx;
const long double eps = 1e-8;
int n;
int x[maxn], y[maxn];
bool check(long double r) {
  long double lmost = -16 * ubound - r, rmost = 16 * ubound + r;
  for (int i = 1; i <= n; i++) {
    if (r * 2 - y[i] < -eps) return false;
    lmost = max(lmost, x[i] - sqrt((r * 2 - y[i]) * y[i]));
    rmost = min(rmost, x[i] + sqrt((r * 2 - y[i]) * y[i]));
  }
  if (rmost - lmost > -eps)
    return true;
  else
    return false;
}
int main() {
  scanf("%d", &n);
  int sign = 0;
  bool isok = true;
  for (int i = 1; i <= n; i++) {
    scanf("%d%d", &x[i], &y[i]);
    if (sign * y[i] < 0) isok = false;
    if (y[i] > 0)
      sign = 1;
    else
      sign = -1;
  }
  if (!isok)
    printf("-1\n");
  else {
    if (sign == -1)
      for (int i = 1; i <= n; i++) y[i] *= -1;
    long double l = 0.5, r = ubound;
    for (int i = 0; i < 500; i++) {
      long double mid = (l + r) / 2;
      if (check(mid))
        r = mid;
      else
        l = mid;
    }
    printf("%.9f\n", double(l));
  }
  return 0;
}
