#include <bits/stdc++.h>
#define _rep(i, x, y) for(int i = x; i <= y; ++i)
#define _req(i, x, y) for(int i = x; i >= y; --i)
#define _rev(i, u) for(int i = head[u]; i; i = e[i].nxt)
#define pb push_back
#define fi first
#define se second
#define mst(f, i) memset(f, i, sizeof f)
using namespace std;
#ifdef ONLINE_JUDGE
#define debug(...) 0
#else
#define debug(...) fprintf(stderr, __VA_ARGS__), fflush(stderr)
#endif
typedef long long ll;
typedef pair<ll, ll> PII;
namespace fastio{
    #ifdef ONLINE_JUDGE
    char ibuf[1 << 20],*p1 = ibuf, *p2 = ibuf;
    #define get() p1 == p2 && (p2 = (p1 = ibuf) + fread(ibuf, 1, 1 << 20, stdin), p1 == p2) ? EOF : *p1++
    #else
    #define get() getchar()
    #endif
    template<typename T> inline void read(T &t){
        T x = 0, f = 1;
        char c = getchar();
        while(!isdigit(c)){
            if(c == '-') f = -f;
            c = getchar();
        }
        while(isdigit(c)) x = x * 10 + c - '0', c = getchar();
        t = x * f;
    }
    template<typename T, typename ... Args> inline void read(T &t, Args&... args){
        read(t);
        read(args...);
    }
    template<typename T> void write(T t){
        if(t < 0) putchar('-'), t = -t;
        if(t >= 10) write(t / 10);
        putchar(t % 10 + '0');
    }
    template<typename T, typename ... Args> void write(T t, Args... args){
        write(t), putchar(' '), write(args...);
    }
    template<typename T> void writeln(T t){
        write(t);
        puts("");
    }
    template<typename T> void writes(T t){
        write(t), putchar(' ');
    }
    #undef get
};
using namespace fastio;
#define multitest() int T; read(T); _rep(tCase, 1, T)
namespace Calculation{
    const ll mod = 998244353;
    ll ksm(ll p, ll h){ll base = p % mod, res = 1; while(h){if(h & 1ll) res = res * base % mod; base = base * base % mod, h >>= 1ll;} return res;}
    void dec(ll &x, ll y){x = ((x - y) % mod + mod) % mod;}
    void add(ll &x, ll y){x = (x + y) % mod;}
    void mul(ll &x, ll y){x = x * y % mod;}
    ll sub(ll x, ll y){return ((x - y) % mod + mod) % mod;}
    ll pls(ll x, ll y){return ((x + y) % mod + mod) % mod;}
    ll mult(ll x, ll y){return x * y % mod;}
}
using namespace Calculation;
const int N = 4e5 + 5, inf = 1e9;
const double eps = 1e-7;
ll n, m, suma, sumb, len, lsh[N];
PII a[N], b[N];
ll f[N], g[N], ssum[N], psum[N];
double pre[N], suf[N];
int main(){
    read(n, m);    
    _rep(i, 1, n) read(a[i].fi, a[i].se), a[i].fi += inf, a[i].se += inf, lsh[++len] = a[i].fi, lsh[++len] = a[i].se, suma += a[i].se - a[i].fi;
    _rep(i, 1, m) read(b[i].fi, b[i].se), b[i].fi += inf, b[i].se += inf, lsh[++len] = b[i].fi, lsh[++len] = b[i].se, sumb += b[i].se - b[i].fi;
    sort(lsh + 1, lsh + 1 + len), len = unique(lsh + 1, lsh + 1 + len) - lsh - 1;
    _rep(i, 1, n) a[i].fi = lower_bound(lsh + 1, lsh + 1 + len, a[i].fi) - lsh, a[i].se = lower_bound(lsh + 1, lsh + 1 + len, a[i].se) - lsh; 
    _rep(i, 1, m) b[i].fi = lower_bound(lsh + 1, lsh + 1 + len, b[i].fi) - lsh, b[i].se = lower_bound(lsh + 1, lsh + 1 + len, b[i].se) - lsh;
    _rep(i, 1, n) f[a[i].fi]++, f[a[i].se]--;
    _rep(i, 1, m) g[b[i].fi]++, g[b[i].se]--;
    _rep(i, 1, len) f[i] += f[i - 1], g[i] += g[i - 1];
    double ans = 0;
    if(suma && sumb){
        _rep(i, 2, len){
            pre[i] = pre[i - 1];
            psum[i] = psum[i - 1] + (g[i - 1]) * (lsh[i] - lsh[i - 1]);
            if(g[i - 1]){
                ll len = lsh[i] - lsh[i - 1];
                pre[i] += 1.00 * len / sumb * (1.00 * (lsh[i - 1] + lsh[i]) / 2.00);
            }
        }
        _req(i, len - 1, 1){
            suf[i] = suf[i + 1];
            ssum[i] = ssum[i + 1] + g[i] * (lsh[i + 1] - lsh[i]);
            if(g[i]){
                ll len = lsh[i + 1] - lsh[i];
                suf[i] += 1.00 * len / sumb * (1.00 * (lsh[i] + lsh[i + 1]) / 2.00);
            }
        }
        _rep(i, 1, len - 1){
            int l = lsh[i], r = lsh[i + 1], len = r - l;
            if(!f[i]) continue;
            if(g[i]){
                double p = (1.00 * len / suma) * (1.00 * len / sumb);
                double cur = 1.00 * len / 3.00;
                ans += cur * p;
            }
            double p = 1.00 * len / suma, cur = 1.00 * (l + r) / 2.00;
            // debug("i:%d p:%.3lf cur:%.3lf\n", i, p, cur);
            // debug("%.3lf %.3lf\n", 1.00 * psum[i] / sumb, 1.00 * ssum[i + 1] / sumb);
            // debug("%.3lf %.3lf\n", pre[i], suf[i + 1]);
            ans += (p * cur * (1.00 * psum[i] / sumb) - pre[i] * p);
            ans += (suf[i + 1] * p - p * cur * (1.00 * ssum[i + 1] / sumb));
            // cout << lsh[i] << ' ' << ans << ' ' << cur << ' ' << endl;
        }
    }else if(suma || sumb){
        if(sumb){
            swap(suma, sumb), swap(a, b), swap(f, g);
            swap(n, m);
        }
        // _rep(i, 1, len) cout << f[i] << ' ' << g[i] << endl;
        // _rep(i, 1, n) debug("(%d,%d)\n", a[i].fi, a[i].se);
        _rep(i, 1, m) g[b[i].fi]++;
        _rep(i, 1, len){
            pre[i] = pre[i - 1] + (1.00 / m) * g[i] * lsh[i];
            psum[i] = psum[i - 1] + g[i];
        }
        _req(i, len, 1){
            suf[i] = suf[i + 1] + (1.00 / m) * g[i] * lsh[i];
            ssum[i] = ssum[i + 1] + g[i];
        }
        _rep(i, 1, len - 1){
            int l = lsh[i], r = lsh[i + 1], len = r - l;
            if(!f[i]) continue;
            double p = 1.00 * len / suma, cur = 1.00 * (l + r) / 2.00;
            // cout << pre[i] << ' ' << suf[i + 1] << endl;
            ans += (p * cur * (1.00 * psum[i] / m) - pre[i] * p);
            ans += (suf[i + 1] * p - p * cur * (1.00 * ssum[i + 1] / m));
        }
        // _rep(i, 1, len) cout << psum[i] << ' ' << ssum[i] << ' ' << pre[i] << ' ' << suf[i] << endl;
    }else{
        _rep(i, 1, n) f[a[i].fi]++;
        _rep(i, 1, m) g[b[i].fi]++;
        _rep(i, 1, len){
            pre[i] = pre[i - 1] + (1.00 / m) * g[i] * lsh[i];
            psum[i] = psum[i - 1] + g[i];
        }
        _req(i, len, 1){
            suf[i] = suf[i + 1] + (1.00 / m) * g[i] * lsh[i];
            ssum[i] = ssum[i + 1] + g[i];
        }
        _rep(i, 1, len){
            if(!f[i]) continue;
            double p = 1.00 / n, cur = 1.00 * lsh[i];
            ans += (p * cur * (1.00 * psum[i] / m) - pre[i] * p);
            ans += (suf[i + 1] * p - p * cur * (1.00 * ssum[i + 1] / m));
            // cout << i << ' ' << ans << endl;
        }
    }
    printf("%.10lf\n", ans);
    return 0;
}