#include <map>
#include <set>
#include <list>
#include <array>
#include <cmath>
#include <deque>
#include <queue>
#include <stack>
#include <tuple>
#include <bitset>
#include <cfloat>
#include <memory>
#include <vector>
#include <random>
#include <string>
#include <cassert>
#include <climits>
#include <cstring>
#include <iomanip>
#include <numeric>
#include <iostream>
#include <algorithm>
#include <functional>
#include <unordered_map>
#include <unordered_set>

using namespace std;

#define rep(i, s, e) for (int i = s; i <= e; ++i)
#define pv(a) cout << #a" = " << a << endl
#define pa(a, l, r) cout << #a" : "; rep(_, l, r) cout << a[_] << " \n"[_ == r]

using db = double;

const int inf = 0x3f3f3f3f;
const int N = 1e5 + 10;

bool check(pair <int, int> *a, int n) {
  rep(i, 1, n) if (a[i].first < a[i].second) return true;
  return false;
}

bool bel(pair <int, int> *a, int n, int l, int r) {
  auto it = upper_bound(a + 1, a + n + 1, make_pair(l, inf));
  return (--it)->second >= r;
}

int n, m, k, val[4 * N];
pair <int, int> a[N], b[N];
db ans;

void solve1() {
  db pre = 0, suf = 0;
  rep(j, 1, m) suf += b[j].first;
  for (int i = 1, j = 1; i <= n; ++i) {
    while (j <= m && b[j].first <= a[i].first) {
      suf -= b[j].first, pre += b[j].first;
      ++j;
    }
    ans += (db) (j - 1) * a[i].first - pre + suf - (db) (m - j + 1) * a[i].first;
  }
  ans /= n * m;
}

void solve2() {
  db pre = 0, suf = 0, blen = 0;
  rep(i, 1, n) suf += a[i].first;
  for (int p = 1, i = 1; p < k; ++p) {
    while (i <= n && a[i].first <= val[p]) {
      suf -= a[i].first, pre += a[i].first;
      ++i;
    }
    if (bel(b, m, val[p], val[p + 1])) {
      db len = val[p + 1] - val[p];
      db mid = (db) (val[p] + val[p + 1]) / 2;
      blen += len;
      ans += len * ((i - 1) * mid - pre + suf - (n - i + 1) * mid);
    }
  }
  ans /= n * blen;
}

void solve3() {
  db aps = 0, apl = 0, ass = 0, asl = 0;
  db bps = 0, bpl = 0, bss = 0, bsl = 0;
  rep(i, 1, n) {
    db len = a[i].second - a[i].first;
    db mid = a[i].first + len / 2;
    ass += len * mid, asl += len;
  }
  rep(j, 1, m) {
    db len = b[j].second - b[j].first;
    db mid = b[j].first + len / 2;
    bss += len * mid, bsl += len;
  }
  // pv(ass);
  // pv(asl);
  rep(p, 1, k - 1) {
    db l = val[p], r = val[p + 1];
    db len = r - l, mid = (l + r) / 2;
    bool fa = bel(a, n, l, r), fb = bel(b, m, l, r);
    // cout << "p, l, r = " << p << ' ' << l << ' ' << r << endl;
    if (fa) ass -= len * mid, asl -= len;
    if (fb) bss -= len * mid, bsl -= len;
    if (fa) {
      ans += len * (bpl * mid - bps + bss - bsl * mid);
      if (fb) ans += len * len * len / 3;
    }
    if (fa) aps += len * mid, apl += len;
    if (fb) bps += len * mid, bpl += len;
    // pv(ans);
  }
  ans /= apl * bpl;
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0), cout.tie(0);
  cin >> n >> m;
  rep(i, 1, n) {
    cin >> a[i].first >> a[i].second;
    val[++k] = a[i].first;
    val[++k] = a[i].second;
  }
  rep(i, 1, m) {
    cin >> b[i].first >> b[i].second;
    val[++k] = b[i].first;
    val[++k] = b[i].second;
  }
  sort(a + 1, a + n + 1);
  sort(b + 1, b + m + 1);
  a[0].first = a[0].second = -inf;
  b[0].first = b[0].second = -inf;
  // rep(i, 1, n) cout << a[i].first << ' ' << a[i].second << endl;
  sort(val + 1, val + k + 1);
  k = unique(val + 1, val + k + 1) - val - 1;
  if (!check(a, n) && !check(b, m)) solve1();
  else if (!check(a, n)) solve2();
  else if (!check(b, m)) {
    swap(a, b), swap(n, m);
    solve2();
  } else solve3();
  printf("%.10lf\n", ans);
  return 0;
}