#include <cstdio>
#include <algorithm>
// #define DEBUG
using namespace std;
typedef long long LL;
typedef long double LD;
typedef pair <int, int> pii;
const int N = 1e5 + 5;
pii a[N], b[N];
int z[N*4], zcnt = 0;
inline int lhs(int x) {return lower_bound(z + 1, z + zcnt + 1, x) - z;}
int cnta[N], cntb[N];
int main() {
	int n, m;
	scanf("%d%d", &n, &m);
	int lena = 0, lenb = 0;
	for (int i = 1; i <= n; ++i) {
		scanf("%d%d", &a[i].first, &a[i].second);
		lena += (a[i].second - a[i].first);
		z[++zcnt] = a[i].first, z[++zcnt] = a[i].second;
	}
	
	for (int i = 1; i <= m; ++i) {
		scanf("%d%d", &b[i].first, &b[i].second);
		lenb += (b[i].second - b[i].first);
		z[++zcnt] = b[i].first, z[++zcnt] = b[i].second;
	}

	if (lena && !lenb) swap(a, b), swap(n, m), swap(lena, lenb);

	sort(z + 1, z + zcnt + 1);
	zcnt = unique(z + 1, z + zcnt + 1) - z - 1;

	for (int i = 1; i <= n; ++i) {
		int l = lhs(a[i].first), r = lhs(a[i].second);
		cnta[l]++;
		if (lena) cnta[r]--;
	}

	for (int i = 1; i <= m; ++i) {
		int l = lhs(b[i].first), r = lhs(b[i].second);
		cntb[l]++;
		if (lenb) cntb[r]--;
	}

	for (int i = 1; i <= zcnt; ++i) {
		if (lena) cnta[i] += cnta[i - 1];
		if (lenb) cntb[i] += cntb[i - 1];
	}

	double ans = 0, pre1 = 0, pre2 = 0;
	for (int i = 1; i <= zcnt; ++i) {
		double part2a = lena ? (double(z[i + 1] + z[i]) / 2.0 * (z[i + 1] - z[i])) : z[i];
		double part1a = lena ? (z[i + 1] - z[i]) : 1;
		double part2b = lenb ? (double(z[i + 1] + z[i]) / 2.0 * (z[i + 1] - z[i])) : z[i];
		double part1b = lenb ? (z[i + 1] - z[i]) : 1;
		if (cnta[i]) {
			ans += pre1 * part2a - pre2 * part1a;
		}
		if (cntb[i]) {
			pre1 += part1b, pre2 += part2b;
		}
		if (cnta[i] && cntb[i] && lena && lenb) {
			ans += double(z[i + 1] - z[i]) * (z[i + 1] - z[i]) / 3.0 * (z[i + 1] - z[i]);
		}
	}
	#ifdef DEBUG
	printf("half result %.12lf\n", ans / (lena ? lena : n) / (lenb ? lenb : m));
	#endif

	double suf1 = 0, suf2 = 0;
	for (int i = zcnt; i > 0; --i) {
		double part2a = lena ? (double(z[i + 1] + z[i]) / 2.0 * (z[i + 1] - z[i])) : z[i];
		double part1a = lena ? (z[i + 1] - z[i]) : 1;
		double part2b = lenb ? (double(z[i + 1] + z[i])) / 2.0 * (z[i + 1] - z[i]) : z[i];
		double part1b = lenb ? (z[i + 1] - z[i]) : 1;
		if (cntb[i] && !lena) suf1 += part1b, suf2 += part2b;
		if (cnta[i]) {
			ans += suf2 * part1a - suf1 * part2a;
		}
		if (cntb[i] && lena) suf1 += part1b, suf2 += part2b;
	}
	printf("%.12lf", ans / (lena ? lena : n) / (lenb ? lenb : m));
	return 0;
}