#include <bits/extc++.h>
using namespace std;

//#define int long long

#define pii pair<int, int>

void prev_greater(vector<int>& r, const vector<int>& a) {
	stack<int> s;
	for (int i = 0; i < a.size(); i++) {
		while (!s.empty() && a[s.top()] <= a[i]) {
			s.pop();
		}
		r[i] = s.empty() ? -1 : s.top();
		s.push(i);
	}
}

void prev_less(vector<int>& r, const vector<int>& a) {
	stack<int> s;
	for (int i = 0; i < a.size(); i++) {
		while (!s.empty() && a[s.top()] >= a[i]) {
			s.pop();
		}
		r[i] = s.empty() ? -1 : s.top();
		s.push(i);
	}
}

void next_greater(vector<int>& r, const vector<int>& a) {
	stack<int> s;
	for (int i = a.size() - 1; i >= 0; i--) {
		while (!s.empty() && a[s.top()] <= a[i]) {
			s.pop();
		}
		r[i] = s.empty() ? a.size() : s.top();
		s.push(i);
	}
}

void next_less(vector<int>& r, const vector<int>& a) {
	stack<int> s;
	for (int i = a.size() - 1; i >= 0; i--) {
		while (!s.empty() && a[s.top()] >= a[i]) {
			s.pop();
		}
		r[i] = s.empty() ? a.size() : s.top();
		s.push(i);
	}
}

signed main() {
#ifdef CB
	ifstream fin("be2.txt");
	cin.rdbuf(fin.rdbuf());
	ofstream fout("ki.txt");
#endif
	int A, B;
	cin >> A >> B;
	vector<int> a(A), b(B);
	for (int i = 0; i < A; i++) {
		cin >> a[i];
	}
	for (int i = 0; i < B; i++) {
		cin >> b[i];
	}
	vector<int> pa(A), na(A);
	vector<int> pb(B), nb(B);
	prev_less(pa, a);
	next_less(na, a);
	prev_greater(pb, b);
	next_greater(nb, b);
	vector<int> da(A), db(B);
	for (int i = 0; i < A; i++) {
		da[i] = na[i] - pa[i] - 1;
	}
	for (int i = 0; i < B; i++) {
		db[i] = nb[i] - pb[i] - 1;
	}
	vector<int> ib(B);
	iota(ib.begin(), ib.end(), 0);
	sort(ib.begin(), ib.end(), [&](int i, int j) { return b[i] < b[j]; });
	vector<int> mb(B + 1);
	for (int i = 0; i < B; i++) {
		mb[i + 1] = max(mb[i], db[ib[i]]);
	}
	sort(b.begin(), b.end());
	int ans = 0;
	for (int i = 0; i < A; i++) {
		auto j = upper_bound(b.begin(), b.end(), a[i]);
		ans = max(ans, da[i] * mb[j - b.begin()]);
	}
	cout << ans << endl;
	return 0;
}