#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define For(i,l,r) for(int i=(int)(l);i<=(int)(r);i++)
const int N=100005;
#define ld double
int n,m,q[N<<4];
int con[2];
ll tot[2];
#define pb push_back
#define PI pair<int,int>
#define fi first
#define se second
#define mp make_pair
vector<PI> v[2];
ld solve(int o){
    ld ans=0;
    unsigned cur=0;
    for(auto [l,r]:v[o^1]){
        int sum=0;
        while(cur<v[o].size()&&v[o][cur].se<=l){sum+=con[o]?v[o][cur].se-v[o][cur].fi:1; cur++;}
        ans+=(ld)sum/tot[o]*(r+l)/2;
        if(cur<v[o].size()&&v[o][cur]==mp(l,r)){
            ans+=(ld)(r-l)/6;
            sum+=con[o]?r-l:1;
            cur++;
        }
        //cerr<<cur<<" "<<sum<<" "<<ans<<endl;
        ans-=(ld)(tot[o]-sum)/tot[o]*(r+l)/2;
    }
    return ans;
}
int main(){
    ios::sync_with_stdio(0); cin.tie(0);
    cin>>n>>m;
    vector<int> q;
    vector<PI> qj[2];
    For(o,0,1)For(i,1,n){
        int l,r;
        cin>>l>>r;
        q.pb(l); q.pb(r);
        con[o]|=r-l;
        tot[o]+=r-l;
        qj[o].pb(mp(l,r));
    }
    For(o,0,1)sort(qj[o].begin(),qj[o].end());
    sort(q.begin(),q.end());
    For(o,0,1){
        unsigned cur=0;
        For(i,0,n-1){
            int L=qj[o][i].fi,R=qj[o][i].se;
            while(cur<q.size()&&q[cur]<=L)cur++;
            while(cur<q.size()&&q[cur]<R){
                v[o].pb(mp(L,q[cur]));
                L=q[cur];
                cur++;
            }
            v[o].pb(mp(L,R));
        }
    }
    For(o,0,1)if(!con[o])tot[o]=n;
    For(o,0,1)sort(v[o].begin(),v[o].end());
    ld ans=0;
    For(o,0,1)ans+=solve(o);
    printf("%.10f\n",ans);
}