#include <bits/stdc++.h>
#define X first
#define Y second
#define rep(i, a, b) for(int i = a; i <= b; i++)
#define pb push_back
using namespace std;
using ld = long double;
typedef long long int ll;
using pii = pair<int, int>;
constexpr int maxn = 4e5 + 10, B = 233, mod = 1e9 + 7;
const ll inf = 1145141919810520131L;
int n, m, p = 0, L = 1, R = 0; ll a[maxn], b[maxn], c[maxn], d[maxn];
struct Node { int cnt; ll mx, sum; Node() { mx = -inf, sum = cnt = 0; } } t[maxn];
#define ls(x) (x << 1)
#define rs(x) (x << 1 | 1)
#define mx(x) (t[x].mx)
#define cnt(x) (t[x].cnt)
#define sum(x) (t[x].sum)
#define mid (l + r >> 1)
inline void up(int x) { 
	mx(x) = max(mx(ls(x)), mx(rs(x)));
	cnt(x) = cnt(ls(x)) + cnt(rs(x)); sum(x) = sum(ls(x)) + sum(rs(x));
}
void mdf(int l, int r, int v, int w, int x) {
	if (l == r) return cnt(x) += w, sum(x) += c[l] * w, mx(x) = (cnt(x) ? c[l] : -inf), void();
	v <= mid ? mdf(l, mid, v, w, ls(x)) : mdf(mid + 1, r, v, w, rs(x)); up(x);
}
ll qry(int l, int r, int s, int x) {
	if (l == r) {
		int pl = s + 1, pr = min(m, s + cnt(x)), u = s;
		if (pl <= pr) u = lower_bound(b + pl, b + pr + 1, c[l], greater<ll>()) - b - 1;
		//cout << l << " " << r << " " << L << " " << R << " " << u << " " << b[u] << " " << c[l] << " " << s << " " << d[u] + (ll)(s + cnt(x) - u) * c[l] << "\n";
		return d[u] + (ll)(s + cnt(x) - u) * c[l];
	}
	return s + cnt(ls(x)) <= m && mx(ls(x)) < b[s + cnt(ls(x))] ? qry(mid + 1, r, s + cnt(ls(x)), rs(x)) : qry(l, mid, s, ls(x)) + sum(rs(x));
}
ll solve(int l, int r, int pl, int pr) {
	if (l > r) return -inf;
	while (R < max(mid, pl) - 1) mdf(1, p, a[++R], 1, 1);
	while (L > mid) mdf(1, p, a[--L], 1, 1);
	while (R > max(mid, pl) - 1) mdf(1, p, a[R--], -1, 1);
	while (L < mid) mdf(1, p, a[L++], -1, 1);
	ll ans = -inf; int u = 0;
	while (R < pr) {
		mdf(1, p, a[++R], 1, 1);
		ll w = qry(1, p, 0, 1);
		if (w > ans) ans = w, u = R;
	}
	return max({ ans, solve(l, mid - 1, pl, u), solve(mid + 1, r, u, pr) });
}
int main() {
	scanf("%d%d", &n, &m);
	for (int i = 1; i <= n; i++) scanf("%lld", &a[i]), c[++p] = a[i];
	for (int i = 1; i <= m; i++) scanf("%lld", &b[i]);
	sort(b + 1, b + m + 1, greater<ll>());
	for (int i = 1; i <= m; i++) d[i] = d[i - 1] + b[i];
	sort(c + 1, c + p + 1), p = unique(c + 1, c + p + 1) - c - 1;
	for (int i = 1; i <= n; i++) a[i] = lower_bound(c + 1, c + p + 1, a[i]) - c;
	printf("%lld\n", solve(1, n, 1, n));
	return 0;
}