#include<bits/stdc++.h>
using namespace std;
const int N = 100010;
const double eps = 1e-8;
int n, m;
struct node{
    double l,r;
    double mid;
    bool operator < (const node &rhs){return l<rhs.l;}
}a[N], b[N];
double suma, sumb;
double calc(double l1,double r1,double l2,double r2){
    if (l1>l2 || (l1==l2 && r1>r2)) swap(l1,l2), swap(r1,r2);
//    printf("lr=%d %d %d %d\n",l1,r1,l2,r2);
    double tmp1=0, tmp2=0, tmp3=0;
    if (r2!=l2) tmp1=1.0*(r2-r1)/(r2-l2)*(1.0*(r1+r2)/2-1.0*(r1+l1)/2);
    if (r2!=l2 && l2!=l1) tmp2=1.0*(r1-l2)/(r2-l2)*(l2-l1)/(r1-l1)*(1.0*(r1+l2)/2-1.0*(l1+l2)/2);
    if (r1!=l1 && r2!=l2) tmp3=1.0/3*(r1-l2)*(r1-l2)*(r1-l2)/(r1-l1)/(r2-l2);
//    printf("c1 %.10lf %.10lf %.10lf\n",tmp1,tmp2,tmp3);
    return tmp1+tmp2+tmp3;
}
double calc2(double l1,double r1,double l2,double r2){
    if (l1>l2 || (l1==l2 && r1<r2)) swap(l1,l2), swap(r1,r2);
//    printf("lr=%d %d %d %d\n",l1,r1,l2,r2);
    double tmp1=0, tmp2=0, tmp3=0;
    if (r1!=l1) {
        tmp1=1.0*(r2-l2)/(r1-l1)/3*(r2-l2);
        tmp2=1.0*(l2-l1)/(r1-l1)*(1.0*(l2+r2)/2-1.0*(l1+l2)/2);
        tmp3=1.0*(r1-r2)/(r1-l1)*(1.0*(r1+r2)/2-1.0*(l2+r2)/2);
    }
//    printf("c2 %.10lf %.10lf %.10lf\n",tmp1,tmp2,tmp3);
    return tmp1+tmp2+tmp3;
}
double pre[N], suf[N];
double pres[N], sufs[N];
bool conc(double l1,double r1,double l2,double r2){
    return (l1<=l2 && r2<=r1) || (l2<=l1 && r1<=r2);
}
bool inter(double l1,double r1,double l2,double r2){
    return (l2<=r1 && l1<=r2);
}
int main(){
    cin>>n>>m;
    for (int i=1;i<=n;++i) cin>>a[i].l>>a[i].r, a[i].r+=eps, a[i].mid=1.0*(a[i].l+a[i].r)/2, suma+=a[i].r-a[i].l;
    for (int i=1;i<=m;++i) cin>>b[i].l>>b[i].r, b[i].r+=eps, b[i].mid=1.0*(b[i].l+b[i].r)/2, sumb+=b[i].r-b[i].l;
//    printf("%.10lf\n",calc(a[1].l,a[1].r,b[1].l,b[1].r));
//    printf("%.10lf\n",calc2(a[1].l,a[1].r,b[1].l,b[1].r));
    sort(a+1,a+1+n); sort(b+1,b+1+m);
    if (a[1].l>b[1].l){
        for (int i=1;i<=max(n,m);++i) swap(a[i],b[i]);
        swap(n,m); swap(suma,sumb);
    }
    for (int i=1;i<=m;++i) pre[i]=pre[i-1]+1.0*(b[i].r-b[i].l)/sumb*b[i].mid, pres[i]=pres[i-1]+(b[i].r-b[i].l)/sumb;
    for (int i=m;i>=1;--i) suf[i]=suf[i+1]+1.0*(b[i].r-b[i].l)/sumb*b[i].mid, sufs[i]=sufs[i+1]+(b[i].r-b[i].l)/sumb;
    double ans=0;
    for (int i=1,L=1,R=1;i<=n;++i){
        double p1=1.0*(a[i].r-a[i].l)/suma;
        while(L<=m && b[L].r<a[i].l) ++L; R=L;
//        printf("i=%d L=%d R=%d\n",i,L,R);
        if (L<=m && inter(a[i].l,a[i].r,b[L].l,b[L].r)){
            R=L;
            while(R<=m && inter(a[i].l,a[i].r,b[R].l,b[R].r)) ++R;
            R--;
            for (int j=L;j<=R;++j){
                double p2=1.0*(b[j].r-b[j].l)/sumb;
//                printf("i=%d j=%d p1=%.10lf p2=%.10lf\n",i,j,p1,p2);
                if (conc(a[i].l,a[i].r,b[j].l,b[j].r)) ans+=p1*p2*calc2(a[i].l,a[i].r,b[j].l,b[j].r);
                else ans+=p1*p2*calc(a[i].l,a[i].r,b[j].l,b[j].r);
            }
            ans+=p1*((a[i].mid*pres[L-1]-pre[L-1])+(suf[R+1]-a[i].mid*sufs[R+1]));
            L=R;
        }
        else {
//            printf("L=%d suf=%.10lf\n",L,suf[L]-a[i].mid*(m+1-L));
            ans+=p1*((a[i].mid*pres[L-1]-pre[L-1])+(suf[L]-a[i].mid*sufs[L]));
        }
//        printf("i=%d L=%d R=%d\n",i,L,R);
    }
    printf("%.10lf\n",ans);
    return 0;
}
/*
1 2
1 2
3 4
5 6

1 1
1 4
2 5

1 1
2 3
1 4
^Z
0.777777777778

2 2
1 2
3 4
1 5
6 7
1.333333333333

1 1
1 2
1 5
^Z
1.583333333333
*/