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*/
#include<bits/stdc++.h>
#define int long long
#define double long double
using namespace std;
const int inf=1e18;
signed main(){
ios::sync_with_stdio(false);
cin.tie(0);
int n,m;
cin>>n>>m;
vector<array<int,2>>a(n),b(m);
int ans1=0,ans2=0;
for(auto &[x,y]:a) cin>>x>>y,ans1+=y-x;
for(auto &[x,y]:b) cin>>x>>y,ans2+=y-x;
sort(a.begin(),a.end());
sort(b.begin(),b.end());
if(!ans1) ans1=1.0L0L/n;
if(!ans2) ans2=1.0L0L/m;
double res=0;
auto cal1=[&]()->void{
int j=0;
double c0=0,c1=0,c2=0,cc0=0;
for(int i=0;i<a.size();++i){
while(j<b.size() && b[j][1]<=a[i][0]){
if(b[j][0]==b[j][1]) c0+=b[j][0],cc0+=1;
else{
c1+=b[j][1]-b[j][0];
c2+=b[j][1]*b[j][1]-b[j][0]*b[j][0];
}
j++;
}
if(a[i][0]==a[i][1]) res+=(cc0*a[i][0]-c0+1.0L*a[i][0]*c1-1.0L*c2/2)/ans1/ans2;
else{
res+=(1.0L*a[i][1]*a[i][1]-1.0L*a[i][0]*a[i][0])*cc0/2/ans1/ans2;
res+=(1.0L*a[i][1]*a[i][1]-1.0L*a[i][0]*a[i][0])*c1/2/ans1/ans2;
res-=(1.0L*a[i][1]-a[i][0])*c0/ans1/ans2;
res-=(1.0L*a[i][1]-a[i][0])*1.0L*c2/2/ans1/ans2;
}
}
};
cal1();
swap(a,b);
cal1();
swap(a,b);
vector<array<int,2>>c;
for(int i=0;i<n;++i){
int x=lower_bound(b.begin(),b.end(),a[i])-b.begin();
if(x){
if(b[x-1][1]>a[i][0]) c.push_back({i,x-1});
}
while(x<m && b[x][0]<a[i][1]){
c.push_back({i,x});
x++;
}
}
auto cal2=[&](array<int,2>a,array<int,2>b)->void{
if(a>b) swap(a,b);
double l1=a[0],r1=a[1],l2=b[0],r2=b[1];
if(a[0]!=a[1] && b[0]!=b[1]){
if(l1<l2){
res+=(1.0L*(l2-l1)*(r2*r2-l2*l2)-1.0L*(r2-l2)*(l2*l2-l1*l1))/2/ans1/ans2;
}
if(r2<r1){
res+=(1.0L*(r2-l2)*(r1*r1-r2*r2)-1.0L*(r1-r2)*(r2*r2-l2*l2))/2/ans1/ans2;
}
if(r2<=r1){
res+=(1.0L*r2*r2*r2-1.0L*l2*l2*l2)/3/ans1/ans2;
res+=(1.0L*(r2-l2)*(r2*r2+l2*l2)-1.0L*(l2+r2)*(r2*r2-l2*l2))/2/ans1/ans2;
}
if(r2>r1){
res+=(1.0L*r1*r1*r1-1.0L*l2*l2*l2)/3/ans1/ans2;
res+=(1.0L*(r1-l2)*(r2*r2+l2*l2)-1.0L*(l2+r2)*(r1*r1-l2*l2))/2/ans1/ans2;
}
}
else if(a[0]==a[1] && b[0]==b[1]) res+=fabs(l2-l1)/ans1/ans2;
else{
if(b[0]==b[1]) swap(l1,l2),swap(r1,r2);
double c=l1;
res+=(l1*l1-l1*(l2+r2)+(l2*l2+r2*r2)/2)/ans1/ans2;
}
};
for(auto [x,y]:c) cal2(a[x],b[y]);
cout<<fixed<<setprecision(15)<<res<<"\n";
}