#include<bits/stdc++.h>
#define LL long long
using namespace std;
const int MxN=1000002;
int n,m,t=0,sum1=0,sum2=0,t1=0;
double ans=0,res,suml;
int l[MxN],r[MxN],l1[MxN],r1[MxN],id[MxN],v[MxN];
double val[MxN];
bool u1[MxN],u2[MxN];
template<class T>void read(T &x)
{
	x=0;int f=0;char ch=getchar();
	while(ch<'0' || ch>'9')f|=(ch=='-'),ch=getchar();
	while(ch>='0' && ch<='9')x=(x<<3)+(x<<1)+(ch^48),ch=getchar();
	x=f? -x:x;return ;
}
inline bool cmp(int x,int y)
{
	return v[x]<v[y];
}
int main()
{
	//freopen("A.in","r",stdin);
	read(n),read(m);
	for(int i=1;i<=n+m;++i)read(l[i]),read(r[i]),v[++t1]=l[i],id[t1]=t1,v[++t1]=r[i],id[t1]=t1,(i<=n? sum1:sum2)+=r[i]-l[i];
	//assert(0<=sum1 && sum1<=2000000000 && 0<=sum2 && sum2<=2000000000);
	sort(id+1,id+t1+1,cmp);
	for(int i=1;i<=t1;++i)
	{
		if(i==1 || v[id[i]]^v[id[i-1]])++t,val[t]=v[id[i]];
		(id[i]&1? l[(id[i]+1)>>1]:r[id[i]>>1])=t;
	}
	//for(int i=1;i<=n+m;++i)printf("l[%d]=%d r[%d]=%d\n",i,l[i],i,r[i]);
	int test=0;
	for(int i=1;i<=n+m;++i)test+=r[i]-l[i];
	//assert(0<=test && test<=(n+m)*4);
	for(int i=1;i<=n;++i)for(int j=l[i];j<r[i];++j)/*assert(!u1[j]),*/u1[j]=1;
	for(int i=n+1;i<=n+m;++i)for(int j=l[i];j<r[i];++j)/*assert(!u2[j]),*/u2[j]=1;
	for(int i=1;i<t;++i)if(u1[i] && u2[i])ans+=(val[i+1]-val[i])/3.0*(val[i+1]-val[i])*(val[i+1]-val[i]);
	if(!sum1 && !sum2)
	{
		//puts("yes");
		int cnt1=0,cnt2=0;
		for(int i=1;i<=n+m;++i)/*assert(l[i]==r[i]),*/(i<=n? u1[l[i]]:u2[l[i]])=1;
		for(int i=1;i<=t;++i)
		{
			//printf("val[%d]=%d cnt1:%d cnt2:%d\n",i,val[i],cnt1,cnt2);
			if(u1[i])ans+=cnt2*val[i]-(m-cnt2)*val[i],++cnt1;
			if(u2[i])ans+=cnt1*val[i]-(n-cnt1)*val[i],++cnt2;
		}
		return 0&printf("%.15lf",ans/n/m);
	}
	if(sum1 && sum2)
	{
		//printf("u1:");for(int i=1;i<=t;++i)printf("%d ",u1[i]);puts("");
		//printf("u2:");for(int i=1;i<=t;++i)printf("%d ",u2[i]);puts("");
		res=suml=0;
		for(int i=1;i<t;++i)
		{
			if(u1[i])ans+=(suml*(val[i]+val[i+1])*0.5-res)*(val[i+1]-val[i]);
			if(u2[i])suml+=val[i+1]-val[i],res+=(val[i+1]-val[i])*(val[i+1]+val[i])*0.5;
			//printf("aft %d: suml:%lf res:%lf ans:%lf\n",i,suml,res,ans);
		}
		res=suml=0;
		for(int i=t-1;i;--i)
		{
			if(u1[i])ans+=(res-suml*(val[i]+val[i+1])*0.5)*(val[i+1]-val[i]);
			if(u2[i])suml+=val[i+1]-val[i],res+=(val[i+1]-val[i])*(val[i+1]+val[i])*0.5;
			//printf("aft %d: suml:%lf res:%lf ans:%lf\n",i,suml,res,ans);
		}
		return 0&printf("%.15lf",ans/sum1/sum2);
	}
	if(!sum2)
	{
		swap(n,m),swap(sum1,sum2);
		for(int i=1;i<=n+m;++i)l1[i]=l[i],r1[i]=r[i];
		for(int i=1;i<=m;++i)l[i]=l1[n+i],r[i]=r1[n+i];
		for(int i=m+1;i<=m+n;++i)l[i]=l1[i-m],r[i]=r1[i-m];
		for(int i=1;i<=t;++i)swap(u1[i],u2[i]);
	}
	for(int i=1;i<=n;++i)/*assert(l[i]==r[i]),*/u1[l[i]]=1;
	//printf("u1:");for(int i=1;i<=t;++i)printf("%d ",u1[i]);puts("");
	//printf("u2:");for(int i=1;i<=t;++i)printf("%d ",u2[i]);puts("");
	res=suml=0;
	for(int i=1;i<t;++i)
	{
		if(u2[i])suml+=val[i+1]-val[i],res+=(val[i+1]-val[i])*(val[i+1]+val[i])*0.5;
		if(u1[i+1])ans+=suml*val[i+1]-res;
		//printf("aft %d: %lf %lf")
	}
	res=suml=0;
	for(int i=t-1;i;--i)
	{
		if(u2[i])suml+=val[i+1]-val[i],res+=(val[i+1]-val[i])*(val[i+1]+val[i])*0.5;
		if(u1[i])ans+=res-suml*val[i];
	}
	return 0&printf("%.15lf",ans/n/sum2);
}