#include <bits/stdc++.h>

using namespace std;
using ll = long long;

const int MAXN = 100'001;

int a[MAXN], b[MAXN], bef[MAXN], aft[MAXN], par[MAXN], siz[MAXN], biggest = 1;

int holvan(int u) {
	return par[u] == u ? u : par[u] = holvan(par[u]);
}

void unio(int u, int v) {
	u = holvan(u); v = holvan(v);
	if (u == v) return;
	siz[u] += siz[v];
	biggest = max(biggest, siz[u]);
	par[v] = u;
}

int main() {
	ios::sync_with_stdio(0); cin.tie(0);
	int n, m; cin >> n >> m;

	iota(par, par+MAXN, 0);
	fill(siz, siz+MAXN, 1);

	for (int i = 1; i <= n; i++) cin >> a[i];
	for (int i = 1; i <= m; i++) cin >> b[i];

	vector<int> indices(n);
	iota(indices.begin(), indices.end(), 1);
	sort(indices.begin(), indices.end(), [&](int i, int j){
		return a[i] < a[j];
	});

	stack<int> st;
	for (int i = 1; i <= n; i++) {
		while (!st.empty() && a[st.top()] >= a[i]) st.pop();
		bef[i] = st.empty() ? 0 : st.top();
		st.push(i);
	}
	st = stack<int>();
	for (int i = n; i >= 1; i--) {
		while (!st.empty() && a[st.top()] >= a[i]) st.pop();
		aft[i] = st.empty() ? n+1 : st.top();
		st.push(i);
	}

	int mine = *min_element(b+1, b+m+1);
	priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> pq;

	for (int i = 1; i < m; i++) {
		int w = max(b[i], b[i+1]);
		pq.push({w, i});
	}

	ll ans = 0;
	for (int i : indices) {
		if (a[i] < mine) continue;
		while (!pq.empty() && pq.top().first <= a[i]) {
			unio(pq.top().second, pq.top().second+1);
			pq.pop();
		}
		ll len = (aft[i] - bef[i] - 1);
		ans = max(ans, len * biggest);
	}

	cout << ans << "\n";

	return 0;
}