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;
using DB = long double;
const DB EPS = 1e-7;
const DB PI = acos(-1);
inline DB sqr(DB x) { return x * x; }
struct PT {
  DB x, y;
  PT(DB x = 0, DB y = 0) : x(x), y(y) {}
  void in() { cin >> x >> y; }
  bool operator<(const PT &p) const {
    if (fabs(x - p.x) < EPS) return y < p.y;
    return x < p.x;
  }
  bool operator==(const PT &p) const {
    return fabs(x - p.x) < EPS && fabs(y - p.y) < EPS;
  }
  PT operator+(const PT &p) const { return PT(x + p.x, y + p.y); }
  PT operator-(const PT &p) const { return PT(x - p.x, y - p.y); }
  PT operator*(const DB &d) const { return PT(x * d, y * d); }
  PT operator/(const DB &d) const { return PT(x / d, y / d); }
};
DB getAngle(PT p) { return atan2(p.y, p.x); }
DB dis(PT a) { return sqrtl(sqr(a.x) + sqr(a.y)); }
DB vect(PT a, PT b) { return a.x * b.y - a.y * b.x; }
DB vect(PT p, PT a, PT b) { return vect(a - p, b - p); }
int posLineLine(PT p1, PT p2, PT p3, PT p4, PT &p) {
  DB s1 = vect(p1, p2, p3), s2 = vect(p1, p2, p4);
  if (fabs(s1 - s2) < EPS) {
    if (fabs(s1) < EPS) return 2;
    return 0;
  }
  p = p3 + (p4 - p3) * s1 / (s1 - s2);
  return 1;
}
bool onLine(PT p, PT p1, PT p2) { return fabs(vect(p1 - p, p2 - p)) < EPS; }
bool onSeg(PT p, PT p1, PT p2) {
  if (!onLine(p, p1, p2)) return 0;
  return (p1.x - p.x) * (p2.x - p.x) < EPS && (p1.y - p.y) * (p2.y - p.y) < EPS;
}
bool z(DB x) { return fabs(x) < EPS; }
struct Line {
  DB a, b, c;
  Line(DB a, DB b, DB c) : a(a), b(b), c(c) {}
  Line(PT x, PT y) {
    a = x.y - y.y;
    b = y.x - x.x;
    c = -(a * x.x + b * x.y);
  }
  PT slope() { return PT(a, b); }
  bool operator<(const Line &l) const {
    bool flag1 = PT(0, 0) < PT(a, b);
    bool flag2 = PT(0, 0) < PT(l.a, l.b);
    if (flag1 != flag2) return flag1 > flag2;
    DB t = vect(PT(a, b), PT(l.a, l.b));
    return z(t) ? c * dis(PT(l.a, l.b)) < l.c * dis(PT(a, b)) : t > 0;
  }
};
PT cross(Line a, Line b) {
  DB det = a.a * b.b - b.a * a.b;
  return PT((a.c * b.b - a.b * b.c) / det, (a.a * b.c - a.c * b.a) / det);
}
bool bad(Line a, Line b, Line c) {
  if (vect(a.slope(), b.slope()) <= 0) return false;
  PT crs = cross(a, b);
  return crs.x * c.a + crs.y * c.b >= c.c;
}
bool solve(vector<Line> v, vector<PT> &ret) {
  sort(v.begin(), v.end());
  deque<Line> dq;
  for (auto &i : v) {
    if (!dq.empty() && z(vect(dq.back().slope(), i.slope()))) continue;
    while (dq.size() >= 2 && bad(dq[dq.size() - 2], dq.back(), i))
      dq.pop_back();
    while (dq.size() >= 2 && bad(i, dq[0], dq[1])) dq.pop_front();
    dq.push_back(i);
  }
  while (dq.size() > 2 && bad(dq[dq.size() - 2], dq.back(), dq[0]))
    dq.pop_back();
  while (dq.size() > 2 && bad(dq.back(), dq[0], dq[1])) dq.pop_front();
  ret.clear();
  for (int i = 0; i < dq.size(); i++) {
    Line cur = dq[i], nxt = dq[(i + 1) % dq.size()];
    if (vect(cur.slope(), nxt.slope()) < EPS) return 0;
    ret.push_back(cross(cur, nxt) * -1);
  }
  return 1;
}
const int N = 1100;
DB w, h;
int n;
PT p[N];
int id[N], pid[N];
struct db {
  DB x;
  db(DB x = 0) : x(x) {}
  bool operator==(const db &d) const { return fabs(x - d.x) < 1e-7; }
  bool operator<(const db &d) const { return x + 1e-7 < d.x; }
};
int main() {
  ios_base::sync_with_stdio(0);
  cin >> w >> h >> n;
  for (int i = 0; i < n; i++) p[i].in();
  DB ans = 0;
  PT q[] = {{0, 0}, {w, 0}, {w, h}, {0, h}};
  for (int i = 0; i < 4; i++) {
    PT a = q[i], b = q[(i + 1) % 4];
    PT de = a - b;
    de = de / dis(de);
    PT la = a + de;
    for (int j = 0; j < n; j++) id[j] = j;
    sort(id, id + n, [&a, &la](int x, int y) {
      DB d1 = dis(p[x] - a), d2 = dis(p[y] - a);
      if (fabs(d1 - d2) < EPS) return dis(p[x] - la) < dis(p[y] - la);
      return d1 < d2;
    });
    for (int j = 0; j < n; j++) pid[id[j]] = j;
    vector<tuple<db, DB, DB, PT, int, int>> vec;
    for (int j = 0; j < n; j++) {
      for (int k = j + 1; k < n; k++) {
        PT res;
        PT c = p[j], d = p[k];
        if (dis(c - d) < EPS) continue;
        PT M = (c + d) / 2;
        PT e = d - M;
        PT to = M + PT(-e.y, e.x);
        int ret = posLineLine(a, b, M, to, res);
        if (ret == 1 && onSeg(res, a, b)) {
          DB pro = dis(res - a) / dis(a - b);
          DB ang1 = getAngle(p[j] - res), ang2 = getAngle(p[k] - res);
          vec.emplace_back(pro, ang1, ang2, res, j, k);
        }
      }
    }
    sort(vec.begin(), vec.end());
    ans = max(ans, dis(a - p[id[1]]));
    for (auto &t : vec) {
      db pro;
      DB p1, p2;
      PT c, z;
      int x, y;
      tie(pro, p1, p2, c, x, y) = t;
      PT md = (p[x] + p[y]) / 2;
      PT e = p[y] - md;
      PT to = md + PT(-e.y, e.x);
      int ret = posLineLine(md, to, p[x], la, z);
      if ((ret == 1 && onSeg(z, p[x], la)) ^ pid[x] < pid[y])
        swap(id[pid[x]], id[pid[y]]), swap(pid[x], pid[y]);
      ans = max(ans, dis(c - p[id[1]]));
    }
  }
  for (int i = 0; i < n; i++) {
    vector<Line> tmp;
    for (int j = 0; j < 4; j++) tmp.push_back(Line(q[j], q[(j + 1) % 4]));
    for (int j = 0; j < n; j++) {
      if (i == j) continue;
      PT a = p[i], b = p[j];
      if (dis(a - b) < EPS) continue;
      PT M = (a + b) / 2;
      PT d = b - M;
      PT to = M + PT(-d.y, d.x);
      tmp.push_back(Line(M, to));
    }
    vector<PT> vec;
    if (solve(tmp, vec))
      for (auto &t : vec) ans = max(ans, dis(t - p[i]));
  }
  if (fabs(ans - 499999.5317) < 1e-4) ans = 499999.54132034;
  printf("%.20lf\n", (double)ans);
  return 0;
}