#include <bits/stdc++.h>
using namespace std;
const long long maxn = 500005;
const long long inf = 0x3f3f3f3f3f3f3f3f;
const long long MOD = 100000007;
const double eps = 1e-10;
long long qpow(long long a, long long b) {
  long long tmp = a % MOD, ans = 1;
  while (b) {
    if (b & 1) {
      ans *= tmp, ans %= MOD;
    }
    tmp *= tmp, tmp %= MOD, b >>= 1;
  }
  return ans;
}
long long lowbit(long long x) { return x & -x; }
long long max(long long a, long long b) { return a > b ? a : b; }
long long min(long long a, long long b) { return a < b ? a : b; }
long long mmax(long long a, long long b, long long c) {
  return max(a, max(b, c));
}
long long mmin(long long a, long long b, long long c) {
  return min(a, min(b, c));
}
void mod(long long &a) {
  a += MOD;
  a %= MOD;
}
long long ll(long long p) { return p << 1; }
long long rr(long long p) { return p << 1 | 1; }
long long mm(long long l, long long r) { return (l + r) / 2; }
long long lg(long long x) {
  if (x == 0) return 1;
  return (long long)log2(x) + 1;
}
bool smleql(double a, double b) {
  if (a < b || fabs(a - b) <= eps) return true;
  return false;
}
bool bigeql(double a, double b) {
  if (a > b || fabs(a - b) <= eps) return true;
  return false;
}
bool eql(double a, double b) {
  if (fabs(a - b) < eps) return 1;
  return 0;
}
double len(double a, double b, double c, double d) {
  return sqrt((a - c) * (a - c) + (b - d) * (b - d));
}
bool isp(long long x) {
  if (x == 1) return false;
  if (x == 2) return true;
  for (long long i = 2; i * i <= x; ++i)
    if (x % i == 0) return false;
  return true;
}
inline long long read() {
  char ch = getchar();
  long long s = 0, w = 1;
  while (ch < 48 || ch > 57) {
    if (ch == '-') w = -1;
    ch = getchar();
  }
  while (ch >= 48 && ch <= 57) {
    s = (s << 1) + (s << 3) + ch - 48;
    ch = getchar();
  }
  return s * w;
}
inline void write(long long x) {
  if (x < 0) putchar('-'), x = -x;
  if (x > 9) write(x / 10);
  putchar(x % 10 + 48);
}
long long gcd(long long a, long long b) {
  if (a == 0) return b;
  if (b == 0) return a;
  if (!(a & 1) && !(b & 1))
    return gcd(a >> 1, b >> 1) << 1;
  else if (!(b & 1))
    return gcd(a, b >> 1);
  else if (!(a & 1))
    return gcd(a >> 1, b);
  else
    return gcd(abs(a - b), min(a, b));
}
long long lcm(long long x, long long y) { return x * y / gcd(x, y); }
long long n;
struct point {
  double x, y;
  void read() { cin >> x >> y; }
} p[maxn];
bool chk(double R) {
  double l = -inf, r = inf;
  for (long long i = 1; i <= n; ++i) {
    double x = p[i].x, y = p[i].y;
    if (2 * y * R - y * y < 0.0) return 0;
    double len = sqrt(2 * y * R - y * y);
    if (x - len > r || x + len < l) return 0;
    l = max(l, x - len), r = min(r, x + len);
  }
  return 1;
}
double half(double l, double r) {
  long long cnt = 1000;
  while (cnt--) {
    double m = (l + r) / 2.0;
    if (chk(m))
      r = m;
    else
      l = m;
  }
  return l;
}
signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0), cout.tie(0);
  cout << fixed << setprecision(10);
  cin >> n;
  bool neg = 0, pos = 0;
  for (long long i = 1; i <= n; ++i) {
    p[i].read();
    if (p[i].y > 0.0)
      pos = 1;
    else
      neg = 1;
  }
  if (pos && neg) {
    cout << -1;
    return 0;
  }
  for (long long i = 1; i <= n; ++i) {
    p[i].y = fabs(p[i].y);
  }
  double ans = half(0, 1e17);
  cout << ans;
  return 0;
}
