#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int h, w;
cin >> h >> w;
vector<int> a(h), b(w);
for (int i = 0; i < h; ++i) {
cin >> a[i];
}
for (int j = 0; j < w; ++j) {
cin >> b[j];
}
constexpr int inf = 1e9 + 7;
vector<int> pref(h + 1, inf), suf(h + 1, inf);
vector<int> rows, columns;
for (int i = 0; i < h; ++i) {
pref[i + 1] = min(pref[i], a[i]);
}
for (int i = h - 1; i >= 0; --i) {
suf[i] = min(a[i], suf[i + 1]);
}
for (int i = 0; i < h; ++i) {
if (pref[i] > a[i] || suf[i + 1] > a[i]) {
rows.push_back(i);
}
}
pref.assign(w + 1, inf), suf.assign(w + 1, inf);
for (int i = 0; i < w; ++i) {
pref[i + 1] = min(pref[i], b[i]);
}
for (int i = w - 1; i >= 0; --i) {
suf[i] = min(b[i], suf[i + 1]);
}
for (int i = 0; i < w; ++i) {
if (pref[i] > b[i] || suf[i + 1] > b[i]) {
columns.push_back(i);
}
}
int n = rows.size(), m = columns.size();
vector dp(n, vector<ll>(m));
for (int i = 0; i < n; ++i) {
for (int j = 0; j < m; ++j) {
if (i == 0 && j == 0) {
continue;
}
dp[i][j] = 1e18;
if (i > 0) {
dp[i][j] = dp[i - 1][j] + 1LL * b[columns[j]] * (rows[i] - rows[i - 1]);
}
if (j > 0) {
dp[i][j] = min(dp[i][j], dp[i][j - 1] + 1LL * a[rows[i]] * (columns[j] - columns[j - 1]));
}
}
}
cout << dp[n - 1][m - 1] << '\n';
return 0;
}
