//#pragma GCC optimize(2)
#include <bits/stdc++.h>
#define F first
#define S second
#define endl '\n'
#define int ll
#define IOS ios::sync_with_stdio(false), cin.tie(0), cout.tie(0)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<long double,long double> pii;
//typedef pair<double,double> pdd;
const int N = 4e5+10;
int n,m;
vector<pii> work(vector<pii> a, vector<pii> b)
{
	vector<pii> now;
	vector<int> pos;
	for(auto [l,r]:b)
	{
		pos.push_back(l);
		pos.push_back(r);
	}
	int j = 0;
	for(auto [l,r] : a)
	{
		while(j<pos.size() && pos[j] < l)
		{
			j++;
		}
		if(j<pos.size() && pos[j]>=l && pos[j]<=r)
		{
			while(j<pos.size() && pos[j]<=r)
			{
				if(l!=pos[j]) now.push_back({l,pos[j]});
				l = pos[j];
				j++;
			}
			if(l<r) now.push_back({l,r});
		}
		else if(l!=r) now.push_back({l,r});
	}
	return now;
}
long double sufl[N];
long double suflm[N];
long double prel[N], prelm[N];
void solve()
{
	cin>>n>>m;
	vector<pii> a(n),b(m);
	for(int i=0;i<n;i++)  cin>>a[i].F>>a[i].S;
	for(int i=0;i<m;i++) cin>>b[i].F>>b[i].S;
	sort(a.begin(), a.end()); sort(b.begin(), b.end());
	int flaga = 1;
	for(auto [l,r]:a)
	{
		if(l!=r) flaga = 0;
	}
	int flagb = 1;
	for(auto [l,r]:b)
	{
		if(l!=r) flagb = 0;
	}
	vector<pii> na = a;
	vector<pii> nb = b;
	
	if(flaga == 0) na = work(a,b);
	if(flagb == 0) nb = work(b,a);
	
	
	
	na.erase(unique(na.begin(), na.end()), na.end());
	nb.erase(unique(nb.begin(), nb.end()), nb.end());


	n = na.size();
	m = nb.size();
	
	for(int i=m-1;i>=0;i--)
	{
		sufl[i] = nb[i].S - nb[i].F;
		sufl[i]+=flagb;
		
		suflm[i] = sufl[i]*(nb[i].S + nb[i].F)/2 ;
		
		if(i!=m-1) 
		{
			sufl[i] += sufl[i+1];
			suflm[i] += suflm[i+1];
		}
	}
//	cout<<endl;
//	cout<<sufl[1]<<' '<<suflm[1]<<endl; 
//	cout<<endl;

	long double ans = 0;
	for(int i=0,j=0;i<n;i++)
	{
		while(j<m && nb[j].F < na[i].F)
		{
			j++;
		}
		
		if(j>=m) break;
		auto [l,r] = na[i];
		if(nb[j].F == na[i].F && nb[j].S == na[i].S)
		{
			ans += ((r*r*r - l*l*l)/3.0 + (long double)r*l*l - (long double)l*r*r);
			j++;
		}

		if(j<m) ans+= (r-l+flaga)*(suflm[j] - sufl[j]*(r+l)/2.0);
	}
	
	for(int i=0;i<m;i++)
	{
		prel[i] = nb[i].S - nb[i].F;
		prel[i] += flagb;
		prelm[i] = prel[i]*(nb[i].S + nb[i].F)/2 ;
		if(i!=0) 
		{
			prel[i] += prel[i-1];
			prelm[i] += prelm[i-1];
		}
	}
//	ans = 0;
//	cout<<endl;
	for(int i=0,j=0;i<n;i++)
	{
		while(j<m && nb[j].S < na[i].S)
		{
			j++;
		}
		j--;
		auto [l,r] = na[i];
//		cout<<i<<' '<<j<<endl;
		if(j>=0) ans+= -(r-l+flaga)*(prelm[j] - prel[j]*(r+l)/2.0);
//		cout<<ans<<endl;
		if(j==-1) j=0;
	}
	long double suma = 0;
	long double sumb = 0;
	for(int i=0;i<n;i++)
	{
		suma += na[i].S - na[i].F + flaga;
	}
	for(int i=0;i<m;i++)
	{
		sumb += nb[i].S - nb[i].F + flagb;
	}
	
//	cout<<endl;
//	for(auto [l,r]:na) cout<<l<<' '<<r<<endl;
//	cout<<endl;	
//	cout<<endl;
//	for(auto [l,r]:nb) cout<<l<<' '<<r<<endl;
//	cout<<endl;	
//	cout<<ans<<endl; 
//	cout<<suma*sumb<<endl;
	ans/=(suma*sumb);
	cout<<fixed<<setprecision(10)<<ans;
}
signed main()
{
 	IOS;
	int T = 1;
//	cin>>T;
	while(T--)
	{
		solve();
	}
}