#include <bits/stdc++.h>
using namespace std;
int n, h, f, l, r;
int cmp(double x, double y = 0) {
  return (x <= y + 1e-10) ? (x + 1e-10 < y) ? -1 : 0 : 1;
}
struct point {
  double x, y;
  point(double x = 0, double y = 0) : x(x), y(y) {}
  point operator+(point q) { return point(x + q.x, y + q.y); }
  point operator-(point q) { return point(x - q.x, y - q.y); }
  point operator*(double t) { return point(x * t, y * t); }
  point operator/(double t) { return point(x / t, y / t); }
  double operator*(point q) { return x * q.x + y * q.y; }
  double operator%(point q) { return x * q.y - y * q.x; }
  int cmp(point q) const {
    if (int t = ::cmp(x, q.x)) return t;
    return ::cmp(y, q.y);
  }
  bool operator==(point q) const { return cmp(q) == 0; }
  bool operator!=(point q) const { return cmp(q) != 0; }
  bool operator<(point q) const { return cmp(q) < 0; }
};
vector<point> polys[1010];
double area(vector<point>& T) {
  double s = 0;
  int n = T.size();
  for (int i = 0; i < n; i++) s += T[i] % T[(i + 1) % n];
  return s / 2;
}
int ccw(point p, point q, point r) { return cmp((p - r) % (q - r)); }
double angle(point p, point q, point r) {
  point u = p - q, v = r - q;
  return atan2(u % v, u * v);
}
bool between(point p, point q, point r) {
  return ccw(p, q, r) == 0 && cmp((p - q) * (r - q)) <= 0;
}
bool seg_intersect(point p, point q, point r, point s) {
  point A = q - p, B = s - r, C = r - p, D = s - q;
  int a = cmp(A % C) + 2 * cmp(A % D);
  int b = cmp(B % C) + 2 * cmp(B % D);
  if (a == 3 || a == -3 || b == 3 || b == -3) return false;
  if (a || b || p == r || p == s || q == r || q == s) return true;
  int t = (p < r) + (p < s) + (q < r) + (q < s);
  return t != 0 && t != 4;
}
point line_intersect(point p, point q, point r, point s) {
  point a = q - p, b = s - r, c = point(p % q, r % s);
  return point(point(a.x, b.x) % c, point(a.y, b.y) % c) / (a % b);
}
int in_poly(point p, vector<point>& T) {
  double a = 0;
  int N = T.size();
  for (int i = 0; i < N; i++) {
    if (between(T[i], p, T[(i + 1) % N])) return -1;
    a += angle(T[i], p, T[(i + 1) % N]);
  }
  return cmp(a) != 0;
}
vector<point> poly_intersect(vector<point>& P, vector<point>& Q) {
  int m = Q.size(), n = P.size();
  int a = 0, b = 0, aa = 0, ba = 0, inflag = 0;
  vector<point> R;
  while ((aa < n || ba < m) && aa < 2 * n && ba < 2 * m) {
    point p1 = P[a], p2 = P[(a + 1) % n], q1 = Q[b], q2 = Q[(b + 1) % m];
    point A = p2 - p1, B = q2 - q1;
    int cross = cmp(A % B), ha = ccw(p2, q2, p1), hb = ccw(q2, p2, q1);
    if (cross == 0 && ccw(p1, q1, p2) == 0 && cmp(A * B) < 0) {
      if (between(p1, q1, p2)) R.push_back(q1);
      if (between(p1, q2, p2)) R.push_back(q2);
      if (between(q1, p1, q2)) R.push_back(p1);
      if (between(q1, p2, q2)) R.push_back(p2);
      if (R.size() < 2) return vector<point>();
      inflag = 1;
      break;
    } else if (cross != 0 && seg_intersect(p1, p2, q1, q2)) {
      if (inflag == 0) aa = ba = 0;
      R.push_back(line_intersect(p1, p2, q1, q2));
      inflag = (hb > 0) ? 1 : -1;
    }
    if (cross == 0 && hb < 0 && ha < 0) return R;
    bool t = cross == 0 && hb == 0 && ha == 0;
    if (t ? (inflag == 1) : (cross >= 0) ? (ha <= 0) : (hb > 0)) {
      if (inflag == -1) R.push_back(q2);
      ba++;
      b++;
      b %= m;
    } else {
      if (inflag == 1) R.push_back(p2);
      aa++;
      a++;
      a %= n;
    }
  }
  if (inflag == 0) {
    if (in_poly(P[0], Q)) return P;
    if (in_poly(Q[0], P)) return Q;
  }
  R.erase(unique(R.begin(), R.end()), R.end());
  if (R.size() > 1 && R.front() == R.back()) R.pop_back();
  return R;
}
int main() {
  scanf("%d %d %d", &n, &h, &f);
  int cnt = 0;
  for (int i = 0; i < n; i++) {
    scanf("%d %d", &l, &r);
    polys[cnt].push_back(point(l, h));
    polys[cnt].push_back(
        line_intersect(point(0, f), point(l, h), point(-1, -h), point(1, -h)));
    polys[cnt].push_back(
        line_intersect(point(0, f), point(r, h), point(-1, -h), point(1, -h)));
    polys[cnt].push_back(point(r, h));
    cnt++;
    polys[cnt].push_back(point(r, -h));
    polys[cnt].push_back(
        line_intersect(point(0, -f), point(r, -h), point(-1, h), point(1, h)));
    polys[cnt].push_back(
        line_intersect(point(0, -f), point(l, -h), point(-1, h), point(1, h)));
    polys[cnt].push_back(point(l, -h));
    cnt++;
  }
  double ans = 0.0;
  for (int i = 0; i < cnt; i++) ans += area(polys[i]);
  for (int i = 0; i < cnt; i++)
    for (int j = i + 1; j < cnt; j++) {
      vector<point> p = poly_intersect(polys[i], polys[j]);
      ans -= area(p);
    }
  printf("%.10f\n", ans);
  return 0;
}
