#include<bits/stdc++.h>
using namespace std;
using ld = long double;
using ll = long long;


ld qi(pair<ll,ll> a,pair<ll,ll> b){
    if(a>b)swap(a,b);
    if(a==b){
        return (a.second-a.first)*1.0/3;
    }

    if(b.first>=a.second){
        return ((b.second + b.first) - (a.second + a.first))*1.0/2;
    }

    if(b.second<=a.second){//包含
        ld u = b.first - a.first;
        ld v = b.second - b.first;
        ld w = a.second - b.second;
        ld res = 0;
        res += (v/2+u/2)*u + v*(v/3) + w*(w/2 + v/2);
        res /= (u+v+w);
        return res; 
    }else{//相交
        ld u = b.first - a.first;
        ld v = a.second - b.first;
        ld w = b.second - a.second;
        ld res = 0;
        res = u*(v+w+u)/2 + v*(v*v/3+w*(w+v)/2)/(v+w);
        res /= (u+v);
        return res;
    }


}

int main(){
    int n,m;cin>>n>>m;
    vector<pair<int,int> > vc1(n);
    vector<pair<int,int> > vc2(m);
    for(auto &it:vc1)cin>>it.first>>it.second;
    for(auto &it:vc2)cin>>it.first>>it.second;
    sort(vc1.begin(),vc1.end());
    sort(vc2.begin(),vc2.end());

    ld ans = 0;
    int p = 0,q = 0;
    ld sm1 = 0,sm2 = 0;
    for(auto it:vc2)sm2+=(it.second+it.first)*1.0/2;

    for(auto it:vc1){
        while (p<vc2.size()&&vc2[p].second<=it.first)
        {
            sm1 += (vc2[p].first+vc2[p].second)*1.0/2;
            p++;
        }
        
        while(q<vc2.size()&&vc2[q].first<=it.second){
            sm2 -= (vc2[q].first+vc2[q].second)*1.0/2;
            q++;
        }
        ld uu = 0;
        uu += p*(it.first+it.second)*1.0/2 - sm1;
        uu += sm2 - (it.first+it.second)*1.0/2 * (vc2.size()-q);
        for(int i = p ; i< q;++i){
            uu += qi(it,vc2[i]);
        }
        uu/=vc2.size();
        ans += uu/vc1.size();
    }

    cout<<fixed<<setprecision(13)<<ans;

    // system("pause");
}