Problem: Gena doesn't like geometry, so he asks you to solve this problem for him.

A rectangle with sides parallel to coordinate axes contains n dots. Let's consider some point of the plane. Let's count the distances from this point to the given n points. Let's sort these numbers in the non-decreasing order. We'll call the beauty of the point the second element of this array. If there are two mimimum elements in this array, the beaty will be equal to this minimum.

Find the maximum beauty of a point inside the given rectangle.

Input

The first line contains three integers w, h, n (1 ≤ w, h ≤ 106, 2 ≤ n ≤ 1000) — the lengths of the rectangle sides and the number of points. Next n lines contain two integers xi, yi (0 ≤ xi ≤ w, 0 ≤ yi ≤ h) each — the coordinates of a point. It is possible that it will be coincident points.

Output

Print a single number — the maximum beauty of a point with the absolute or relative error of at most 10 - 9.

Examples

Input

5 5 4
0 0
5 0
0 5
5 5


Output

4.99999999941792340


Input

5 5 3
4 0
2 5
4 1


Output

5.65685424744772010

Note

The point which beauty we need to find must have coordinates (x, y), where 0 ≤ x ≤ w, 0 ≤ y ≤ h. Some of the n points can coincide.

Solution (in CPP):

Solution:
#include <bits/stdc++.h>
using namespace std;
const int Imx = 2147483647;
const int mod = 1000000007;
const long long Lbig = 2e18;
inline long long getnum() {
  register long long r = 0;
  register bool ng = 0;
  register char c;
  c = getchar();
  while (c != '-' && (c < '0' || c > '9')) c = getchar();
  if (c == '-') ng = 1, c = getchar();
  while (c >= '0' && c <= '9') r = r * 10 + c - '0', c = getchar();
  if (ng) r = -r;
  return r;
}
template <class T>
inline void putnum(T x) {
  if (x < 0) putchar('-'), x = -x;
  register short a[20] = {}, sz = 0;
  while (x > 0) a[sz++] = x % 10, x /= 10;
  if (sz == 0) putchar('0');
  for (int i = sz - 1; i >= 0; i--) putchar('0' + a[i]);
}
inline void putsp() { putchar(' '); }
inline void putendl() { putchar('\n'); }
inline char mygetchar() {
  register char c = getchar();
  while (c == ' ' || c == '\n') c = getchar();
  return c;
}
const double eps = 1e-9;
const double pi = acos(-1);
bool is0(double x) { return x > -eps && x < eps; }
struct point {
  double x, y;
  point(double _x = 0, double _y = 0) {
    x = _x;
    y = _y;
  }
  point operator+(const point &t) const { return point(x + t.x, y + t.y); }
  point operator-(const point &t) const { return point(x - t.x, y - t.y); }
  point operator*(const point &t) const {
    return point(x * t.x - y * t.y, x * t.y + y * t.x);
  }
  point operator*(const double &t) const { return point(x * t, y * t); }
  point operator-() const { return point(-x, -y); }
  double len() const { return sqrt(x * x + y * y); }
  point operator/(const point &t) const {
    return point(x * t.x + y * t.y, -x * t.y + y * t.x) / t.len() / t.len();
  }
  point operator/(const double &t) const { return point(x / t, y / t); }
  double det(const point &t) const { return x * t.y - y * t.x; }
  double dot(const point &t) const { return x * t.x + y * t.y; }
  double sqrl() const { return x * x + y * y; }
  point unit() const { return (*this) / len(); }
  bool operator<(const point &t) const {
    return is0(x - t.x) ? y < t.y : x < t.x;
  }
  bool operator==(const point &t) const { return is0(x - t.x) && is0(y - t.y); }
  void out() { cout << x << "," << y << endl; }
  void in() { cin >> x >> y; }
  double rad() { return atan2(y, x); }
  point conj(const point &p) { return point(p.x, -p.y); }
  point rot90() { return point(-y, x); }
};
double area(double x, double y, double z) {
  double p = (x + y + z) / 2;
  return sqrt(p * (p - x) * (p - y) * (p - z));
}
bool parallel(const point &px, const point &py, const point &qx,
              const point &qy) {
  return is0((px - py).det(qx - qy));
}
point intersection(const point &px, const point &py, const point &qx,
                   const point &qy) {
  double t = -(px - qx).det(qy - qx) / (py - px).det(qy - qx);
  return px + (py - px) * t;
}
point intersection(const pair<point, point> &p, const pair<point, point> &q) {
  return intersection(p.first, p.second, q.first, q.second);
}
bool insegcross(const point &px, const point &py, const point &qx,
                const point &qy) {
  if (parallel(px, py, qx, qy)) return false;
  point p = intersection(px, py, qx, qy);
  return (px - p).dot(py - p) < -eps && (qx - p).dot(qy - p) < -eps;
}
const int tbmxsz = 111;
point tmppt[tbmxsz];
int tb[tbmxsz], tbn;
void calcchull(point a[], int n) {
  tbn = 0;
  int t[tbmxsz], tn;
  tn = 0;
  for (int i = 1; i <= n; i++) {
    t[tn++] = i;
    while (tn > 2 &&
           (a[tn - 2] - a[tn - 3]).det(a[tn - 1] - a[tn - 3]) > -eps) {
      a[tn - 2] = a[tn - 1];
      tn--;
    }
  }
  for (int i = 0; i < tn; i++) tb[tbn++] = t[i];
  tn = 0;
  for (int i = 1; i <= n; i++) {
    t[tn++] = i;
    while (tn > 2 && (a[tn - 2] - a[tn - 3]).det(a[tn - 1] - a[tn - 3]) < eps) {
      a[tn - 2] = a[tn - 1];
      tn--;
    }
  }
  for (int i = tn - 2; i > 0; i--) tb[tbn++] = t[i];
}
int makechull(point a[], int n) {
  for (int i = 1; i <= n; i++) tmppt[i] = a[i];
  calcchull(a, n);
  for (int i = 1; i <= tbn; i++) a[i] = tmppt[tb[i - 1]];
  return tbn;
}
pair<point, point> circleinter(point p, double pr, point q, double qr) {
  double c =
      (p.x * p.x - q.x * q.x + p.y * p.y - q.y * q.y - pr * pr + qr * qr) / 2;
  point p1, p2;
  if (is0(p.x - q.x)) {
    p1 = point(0, c / (p.y - q.y));
    p2 = point(1, c / (p.y - q.y));
  } else {
    p1 = point(c / (p.x - q.x), 0);
    p2 = point((c - (p.y - q.y)) / (p.x - q.x), 1);
  }
  point O = intersection(p1, p2, p, q);
  double len = sqrt(pr * pr - (p - O).sqrl());
  return make_pair(O + (p - q).rot90().unit() * len,
                   O + (q - p).rot90().unit() * len);
}
point a[1011];
int w, h, n;
vector<pair<double, int> > v;
bool check(int cur, double R) {
  point p = a[cur];
  v.clear();
  int st = 0;
  a[n + 1] = point(2 * w - p.x, p.y);
  a[n + 2] = point(p.x, 2 * h - p.y);
  a[n + 3] = point(-p.x, p.y);
  a[n + 4] = point(p.x, -p.y);
  for (int i = 1; i <= n + 4; i++) {
    if (i == cur) continue;
    if ((a[i] - p).len() > 2 * R) continue;
    double l, r;
    if ((a[i] - p).len() < eps) {
      if (i == n + 1)
        l = -pi / 2, r = pi / 2;
      else if (i == n + 2)
        l = 0, r = pi;
      else if (i == n + 3)
        l = pi / 2, r = -pi / 2;
      else if (i == n + 4)
        l = pi, r = 0;
      else
        continue;
    } else {
      pair<point, point> pp = circleinter(p, R, a[i], R);
      l = (pp.first - p).rad(), r = (pp.second - p).rad();
    }
    int c = 1 + (i > n);
    if (l < r) {
      v.push_back(make_pair(l, +c));
      v.push_back(make_pair(r, -c));
    } else {
      st += c;
      v.push_back(make_pair(r, -c));
      v.push_back(make_pair(l, c));
    }
  }
  sort(v.begin(), v.end());
  int cnt = st;
  if (st <= 1) return true;
  for (int i = 0; i < v.size() && v[i].first + eps < pi; i++) {
    cnt += v[i].second;
    if (cnt <= 1) return true;
  }
  return false;
}
pair<int, int> tmpa[1011];
int main() {
  w = getnum(), h = getnum(), n = getnum();
  for (int i = 1; i <= n; i++) scanf("%lf%lf", &a[i].x, &a[i].y);
  srand(time(NULL));
  random_shuffle(a + 1, a + n + 1);
  double ans = 0;
  for (int i = 1; i <= n; i++) {
    if (!check(i, ans + ans * eps)) continue;
    double l = ans, r = 2e6;
    for (int j = 0; j < 59; j++) {
      if (check(i, (l + r) / 2))
        l = (l + r) / 2;
      else
        r = (l + r) / 2;
    }
    ans = l;
  }
  printf("%.10lf\n", ans);
  return 0;
}