#include <bits/stdc++.h>

#define maxn 1000005
#define db long double

using namespace std;

int n, m;

struct node {
	int l, r;
}a[maxn], b[maxn];

struct bd {
	int x, p;
}x[maxn];

int tot;

db sa;
db pa;
db sb;
db pb;

db asum;
db bsum;

db ans;

db ap(int len) {
	if (asum == 0) return 1.0 / n;
	return 1.0 * len / asum;
}

db bp(int len) {
	if (bsum == 0) return 1.0 / m;
	return 1.0 * len / bsum;
}

int main() {
//	freopen("dt.in", "r", stdin);
//	freopen("dt.out", "w", stdout);
	scanf("%d%d", &n, &m);
	for (int i = 1; i <= n; i++) {
		scanf("%d%d", &a[i].l, &a[i].r);
		x[++tot] = {a[i].l, 0};
		x[++tot] = {a[i].r, 0};
		asum += a[i].r - a[i].l;
	}
	sort(x + 1, x + tot + 1, [&](bd a, bd b) {return a.x < b.x;});
	for (int i = 1; i <= m; i++) {
		scanf("%d%d", &b[i].l, &b[i].r);
		x[++tot] = {b[i].l, 1};
		x[++tot] = {b[i].r, 1};
		bsum += b[i].r - b[i].l;
	}
	sort(x + 1, x + tot + 1, [&](bd a, bd b) {return a.x < b.x;});
	int flga = 0, flgb = 0;
	for (int i = 1; i < tot; i++) {
		if (x[i].p == 0) flga ^= 1;
		else flgb ^= 1;
		int len = x[i + 1].x - x[i].x;
		db mid = (x[i].x + x[i + 1].x) / 2.0;
		if (flga && flgb) ans += len * ap(len) * bp(len) / 3.0;
		if (flga) {
			ans += (mid * pb - sb) * ap(len);
		}
		if (flgb) {
			ans += (mid * pa - sa) * bp(len);
		}
		if (flga) {
			pa += ap(len);
			sa += ap(len) * mid;
		}
		if (flgb) {
			pb += bp(len);
			sb += bp(len) * mid;
		}
//		cout<<ans<<" "<<pa<<" "<<sa<<endl;
	}
	printf("%.12Lf\n", ans);
	return 0;
}