#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#define int long long
    using namespace std;
    const int N = 500005;
    const int INF = 2e9;
    pair<int, int> a[N], b[N], x[N], y[N];
    double w[N], g[N], f[N];
signed main() {
    int n = 0, m = 0;
    bool flagn = false, flagm = false;
    scanf("%lld%lld", &n, &m);
    for (int i = 1; i <= n; i++) {
        scanf("%lld%lld", &a[i].first, &a[i].second);
        if (a[i].first < a[i].second)
            flagn = true;
    }
    for (int i = 1; i <= m; i++) {
        scanf("%lld%lld", &b[i].first, &b[i].second);
        if (b[i].first <  b[i].second)
            flagm = true;
    }
    sort(a + 1, a + n + 1);
    sort(b + 1, b + m + 1);
    //printf("114514----\n");
    if (!flagn && !flagm) {
        for (int i = 1; i <= m; i++)
            w[i] = w[i - 1] + b[i].first;
        double ans = 0;
        for (int i = 1, j = 1; i <= n; i++) {
            while (j <= m && b[j].first < a[i].first)
                j++;
            ans += (double)((double)a[i].first * (j - 1) - w[j - 1]) / ((double)n * m);
            ans += (double)(w[m] - w[j - 1] - (double)a[i].first * (m - j + 1))/ ((double)n * m);
        }
        printf("%.11f\n", ans);
        return 0;
    }
    //printf("191810\n");
    if (flagn && !flagm) {
        for (int i = 1; i <= max(n, m); i++)
            swap(a[i], b[i]);
        swap(n, m), swap(flagn, flagm);
    }

    if (!flagn && flagm) {
         for (int i = 1; i <= m; i++) {
            w[i] = w[i - 1];
            if (b[i].first < b[i].second)
                w[i] += (double)(b[i].second + b[i].first) * (b[i].second - b[i].first);
            g[i] = g[i - 1] + (b[i].second - b[i].first);
        }
        double ans = 0;
        for (int i = 1, j = 1; i <= n; i++) {
            while (j <= m && b[j].second <= a[i].first)
                j++;
            if (j <= m && b[j].first < a[i].first) {
                ans += ((double)2 * a[i].first * (j - 1) * g[j - 1] - w[j - 1]) / 2.0  / g[m] / n;
                ans += (w[m] - w[j] - (double)2 * a[i].first * (m - j) * (g[m] - g[j])) / 2.0  / g[m] / n;
                ans += ((double)2 * a[i].first - (a[i].first + b[j].first)) / 2.0 * ((double)(a[i].first - b[j].first) / g[m]) / n;
                ans += ((double)a[i].first + b[j].second - 2 * a[i].first) / 2.0 * ((double)(b[j].second - a[i].first) / g[m]) / n;
            } else {
                ans += ((double)2 * a[i].first * (j - 1) * g[j - 1]- w[j - 1]) / 2.0 / g[m] / n;
                ans += (w[m] - w[j - 1] - (double)2 * a[i].first * (m - j + 1) * (g[m] - g[j - 1])) / 2.0  / g[m] / n;
            }
        }
        printf("%.11f\n", ans);
        return 0;
    }
    
    
    int u = 1, v = 1, tn = 0, tm = 0;
    x[0] = y[0] = make_pair(-INF,-INF);
    while (u <= n || v <= m) {
        if (u <= n && a[u].first == a[u].second) {
            u++; continue;
        }
        if (v <= m && b[v].first == b[v].second) {
            v++; continue;
        }

        if (u <= n && v > m)
            tn++, x[tn] = make_pair(max(x[tn - 1].second, a[u].first), a[u].second), u++;
        else if (u <= n && v <= m && a[u] <= b[v] && a[u].second <= b[v].first)
            tn++, x[tn] = make_pair(max(x[tn - 1].second, a[u].first), a[u].second), u++;
        else if (u <= n && v <= m && a[u] <= b[v] && a[u].second > b[v].first) {
            if (a[u] == b[v]) {
                tn++, x[tn] = make_pair(max(x[tn - 1].second, a[u].first), a[u].second);
                tm++, y[tm] = make_pair(max(y[tm - 1].second, b[v].first), b[v].second);
                u++, v++;
            } else if (a[u].first == b[v].first) {
                tn++, x[tn] = make_pair(max(x[tn - 1].second, a[u].first), a[u].second);
                tm++, y[tm] = make_pair(max(y[tm - 1].second, b[v].first), a[u].second);
                b[v].first = a[u].second;
                u++;
            } else {
                tn++, x[tn] = make_pair(max(x[tn - 1].second, a[u].first), b[v].first);
                a[u].first = b[v].first;
            }
        }
        else if (v <= m && u > n)
            tm++, y[tm] = make_pair(max(y[tm - 1].second, b[v].first), b[v].second), v++;
        else if (v <= m && u <= n && b[v] <= a[u] && b[v].second <= a[u].first)
            tm++, y[tm] = make_pair(max(y[tm - 1].second, b[v].first), b[v].second), v++;
        else {
            if (a[u] == b[v]) {
                tn++, x[tn] = make_pair(max(x[tn - 1].second, a[u].first), a[u].second);
                tm++, y[tm] = make_pair(max(y[tm - 1].second, b[v].first), b[v].second);
                u++, v++;
            } else if (a[u].first == b[v].first) {
                tn++, x[tn] = make_pair(max(x[tn - 1].second, a[u].first), b[v].second);
                tm++, y[tm] = make_pair(max(y[tm - 1].second, b[v].first), b[v].second);
                a[u].first = b[v].second;
                v++;
            } else {
                tm++, y[tm] = make_pair(max(y[tm - 1].second, b[v].first), a[u].first);
                b[v].first = a[u].first;
            }
        }
       // printf("%d %d %d %d\n", u, v, tn, tm);
    }
    for (int i = 1; i <= tm; i++) {
        //if (y[i].first < y[i].second)
            w[i] = w[i - 1] + (double)(y[i].first + y[i].second) * (y[i].second - y[i].first);
        g[i] = g[i - 1] + (y[i].second - y[i].first);
    }
    for (int i = 1; i <= tn; i++) {
        f[i] = f[i - 1] + (x[i].second - x[i].first);
    }
    //printf("-------\n");
    double ans = 0;
    for (int i = 1, j = 1; i <= tn; i++) {
        while (j <= tm && y[j].first < x[i].first)
            j++;
        //cout << j << " ---------\n";
        if (j <= tm && y[j] == x[i]) {
            //cout << f[tn] << " " << g[tm] << "   ---\n";
            ans += (x[i].second - x[i].first) / 3.0 * (x[i].second - x[i].first) / f[tn] * (y[i].second - y[i].first) / g[tm];
            ans += ((double)(x[i].second + x[i].first) * (j - 1) * g[j - 1] - w[j - 1]) / 2.0 * (x[i].second - x[i].first) / f[tn] / g[tm];
            ans += (w[tm] - w[j] - (double)(x[i].second + x[i].first) * (tm - j) * (g[tm] - g[j])) / 2.0 * (x[i].second - x[i].first) / f[tn]  / g[tm];
        } else {
            ans += ((double)(x[i].second + x[i].first) * (j - 1) * g[j] - w[j - 1]) / 2.0 * (x[i].second - x[i].first) / f[tn] / g[tm];
            ans += (w[tm] - w[j - 1] - (double)(x[i].second + x[i].first) * (tm - j + 1) * (g[tm] - g[j - 1])) / 2.0 * (x[i].second - x[i].first) / f[tn]  / g[tm];
        }
        
    }  
    printf("%.11f", ans);
    return 0;
}