#include<cstdio>
#include<iostream>
#include<algorithm>
#define int long long
#define RI register int
#define CI const int&
using namespace std;
typedef long long LL;
typedef pair <int,int> pi;
const int N=100005;
int n,m,al[N],ar[N],bl[N],br[N],rst[N*4],cnt,lena,lenb,a[N],b[N];
signed main()
{
	RI i; scanf("%lld%lld",&n,&m);
	for (i=1;i<=n;++i)
	{
		scanf("%lld%lld",&al[i],&ar[i]);
		lena+=ar[i]-al[i];
		rst[++cnt]=al[i]; rst[++cnt]=ar[i];
	}
	for (i=1;i<=m;++i)
	{
		scanf("%lld%lld",&bl[i],&br[i]);
		lenb+=br[i]-bl[i];
		rst[++cnt]=bl[i]; rst[++cnt]=br[i];
	}
	sort(rst+1,rst+cnt+1); cnt=unique(rst+1,rst+cnt+1)-rst-1;
	for (i=1;i<=n;++i)
	{
		int l=lower_bound(rst+1,rst+cnt+1,al[i])-rst;
		int r=lower_bound(rst+1,rst+cnt+1,ar[i])-rst;
		if (l!=r) ++a[l],--a[r]; else ++a[l];
	}
	for (i=1;i<=m;++i)
	{
		int l=lower_bound(rst+1,rst+cnt+1,bl[i])-rst;
		int r=lower_bound(rst+1,rst+cnt+1,br[i])-rst;
		if (l!=r) ++b[l],--b[r]; else ++b[l];
	}
	long double ans=0,pa=0,pb=0,sa=0,sb=0;
	for (i=1;i<=cnt;++i) a[i]+=a[i-1],b[i]+=b[i-1];
	for (i=1;i<=cnt;++i)
	{
		auto PA=[&](CI len)
		{
			if (lena==0) return 1.0L/n;
			else return 1.0L*len/lena;
		};
		auto PB=[&](CI len)
		{
			if (lenb==0) return 1.0L/m;
			else return 1.0L*len/lenb;
		};
		int len=rst[i+1]-rst[i];
		long double mid=(rst[i+1]+rst[i])/2.0L;
		if (a[i]&&b[i]) ans+=1.0L/3.0L*len*len*PA(len)*PB(len);
		if (a[i])
		{
			ans+=PA(len)*pb*(mid-sb);
			sa+=mid*PA(len); pa+=PA(len);
		}
		if (b[i])
		{
			ans+=PB(len)*pa*(mid-sa);
			sb+=mid*PB(len); pb+=PB(len);
		}
	}
	return printf("%.12Lf",ans),0;
}