#include<iostream>
#include<cmath>
#include<algorithm>
#include<cstring>
using namespace std;
int n,m;
const int N=1e5+5;
int min(int a,int b) {
	if(a<b)return a;
	return b;
}
int max(int a,int b) {
	if(a<b)return b;
	return a;
}
struct section {
	int l,r;
	long double mid() {
		return (l+r)/2.0;
	}
	bool operator <(const section &t)const {
		return l<t.l||l==t.l&&r<t.r;
	}
} a[N],b[N],sa[5],sb[5];
typedef long long LL;
typedef long double db;
db prea[N],suba[N];
int lena[N],lenb[N];
db palen(db t) {
	if(lena[n]) return 1.0*t/lena[n];
	else return 1.0/n;
}
db pblen(db t) {
	if(lenb[m]) return 1.0*t/lenb[m];
	else return 1.0/m;
}
int main() {
	scanf("%d%d",&n,&m);
	for(int i=1; i<=n; i++) {
		scanf("%d%d",&a[i].l,&a[i].r);
		lena[i]=lena[i-1]+a[i].r-a[i].l;
	}
	for(int i=1; i<=m; i++) {
		scanf("%d%d",&b[i].l,&b[i].r);
		lenb[i]=lenb[i-1]+b[i].r-b[i].l;
	}
	sort(a+1,a+1+n);
	sort(b+1,b+1+m);
	for(int i=1; i<=n; i++)
		prea[i]=prea[i-1]+a[i].mid();
	for(int i=n; i>=1; i--)
		suba[i]=suba[i+1]+a[i].mid();
	db ans=0;
	for(int i=1; i<=m; i++) {
		int l=b[i].l,r=b[i].r;
		db sum=0,md=b[i].mid();
		int L=1,R=n,t1=0,t2=n+1;
		while(L<=R) {
			int mid=L+R>>1;
			if(a[mid].r<=l)t1=mid,L=mid+1;
			else R=mid-1; 
		}
		sum=sum+(md*t1-prea[t1])*palen(lena[t1])*pblen(r-l);
		L=1,R=n;
		while(L<=R) {
			int mid=L+R>>1;
			if(a[mid].l>=r)R=mid-1,t2=mid;
			else L=mid+1;
		}
		sum=sum+(suba[t2]-md*t2)*palen(lena[n]-lena[t2-1])*pblen(r-l);
		t1++,t2--;
		db g=palen(1)*pblen(1);
		sum*=g;
		for(int j=t1; j<=t2; j++) {
			int al=a[j].l,ar=a[j].r,at=0,bt=0;
			if(al<l) {
				sa[++at]=section{al,l};
			} else if(l<al) {
				sb[++bt]=section{l,al};
			}
			if(ar>r) {
				sa[++at]=section{r,ar};
			}else if(r>ar) {
				sb[++bt]=section{ar,r};
			}
			sa[0]=section{max(al,l),min(ar,r)};
			sb[0]=section{max(al,l),min(ar,r)};
//			printf("[%d %d]\n",at,bt);
			for(int aa=0; aa<=at; aa++) {
				for(int bb=0; bb<=bt; bb++) {
//					printf("[%d %d] [%d %d]\n",sa[aa].l,sa[aa].r,sb[bb].l,sb[bb].r);
					if(sa[aa].l!=sb[bb].l||sa[aa].r!=sb[bb].r) {
//						printf("  sum=%.12Lf\n",sum);
						sum=sum+abs(sa[aa].mid()-sb[bb].mid())*palen(sa[aa].r-sa[aa].l)*pblen(sb[bb].r-sb[bb].l);
//						printf("  sum=%.12Lf\n",sum);
					} else {
						sum=sum+(sa[aa].r-sa[aa].l)/3.0l*palen(sa[aa].r-sa[aa].l)*pblen(sb[bb].r-sb[bb].l);
					}
				}
			}
		}
		ans=ans+sum;
	}
	printf("%.12Lf\n",ans);
	return 0;
}