#include <bits/stdc++.h>

using namespace std;
int n, m;

vector<pair<int, int>> split(const vector<pair<int, int>> &v, const vector<int> &pos)
{
	vector<pair<int, int>> ret;
	for(auto[l, r] : v)
	{
		if(l == r)
		{
			ret.emplace_back(l, r);
			continue;
		}
		int last = l;
		auto it = upper_bound(pos.begin(), pos.end(), l);
		while(it != pos.end() && (*it) <= r)
		{
			ret.emplace_back(last, *it);
			last = *it;
			it++;
		}
	}
	return ret;
}

void build_pref(vector<pair<int, int>> &b, int totb, vector<long long> &pref_exp, vector<long long> &pref_prob)
{
	int m = b.size();
	for(int i = 0; i < m; ++i)
	{
		auto [l, r] = b[i];
		long long E = (r + l);
		long long prob = 1;
		if(totb)
			prob = r - l;
		
		pref_prob.push_back((pref_prob.empty() ? 0 : pref_prob.back()) + prob);
		pref_exp.push_back((pref_exp.empty() ? 0 : pref_exp.back()) + prob * E);
	}
}

long double intr(long double a, long double b)
{
	return (b / 3.0L - a / 3.0L);
}

int main()
{
	ios_base::sync_with_stdio(false), cin.tie(NULL);
	cin >> n >> m;
	vector<pair<int, int>> a(n), b(m);
	int tota = 0, totb = 0;
	for(int i = 0; i < n; ++i)
	{
		cin >> a[i].first >> a[i].second;
		tota += (a[i].second - a[i].first);
	}
	for(int i = 0; i < m; ++i)
	{
		cin >> b[i].first >> b[i].second;
		totb += (b[i].second - b[i].first);
	}
	vector<int> pos;
	for(auto[l, r] : a)
		pos.push_back(l), pos.push_back(r);
	for(auto[l, r] : b)
		pos.push_back(l), pos.push_back(r);
	sort(pos.begin(), pos.end());
	pos.erase(unique(pos.begin(), pos.end()), pos.end());

	a = split(a, pos);
	b = split(b, pos);
	n = a.size();
	m = b.size();
	
	sort(a.begin(), a.end());
	sort(b.begin(), b.end());
	
	vector<long long> pref_exp, pref_prob, suf_exp, suf_prob;
	build_pref(b, totb, pref_exp, pref_prob);
	reverse(b.begin(), b.end());
	build_pref(b, totb, suf_exp, suf_prob);
	reverse(b.begin(), b.end());

	reverse(suf_exp.begin(), suf_exp.end());
	reverse(suf_prob.begin(), suf_prob.end());
	
	long double ans = 0;

	for(int i = 0; i < n; ++i)
	{
		auto [l, r] = a[i];
		long long E = (r + l);
		long double prob = 1.0L;
		if(tota)
			prob = (r - l) * 1.0L;

		int j = lower_bound(b.begin(), b.end(), make_pair(r, -1)) - b.begin();
		
	
		if(j < m)
			ans += prob * (suf_exp[j] - suf_prob[j] * E) / 2.0L;


		if(j > 0)
		{
			long double prob2 = 1.0L;
			long long E2 = b[j - 1].first + b[j - 1].second;
			if(totb)
				prob2 = (b[j - 1].second - b[j - 1].first) * 1.0L;
			if(b[j - 1] == a[i])
			{
				ans += prob * prob2 * intr(l, r);
			}
			else
			{
				ans += prob * prob2 * (E - E2) / 2.0L;
			}

			if(j - 2 >= 0)
				ans += prob * (pref_prob[j - 2] * E - pref_exp[j - 2]) / 2.0L;
		}
	}
	if(tota)
		ans /= tota;
	else
		ans /= n;
	if(totb)
		ans /= totb;
	else
		ans /= m;

	cout << setprecision(20) << fixed << ans << endl;
}