#include <bits/stdc++.h>
using namespace std;
#define InTheNameOfGod ios::sync_with_stdio(0);cin.tie(0); cout.tie(0);
using ll = long long;

const ll maxN = 2e5 + 5;
const ll MOD = 1e9 + 7;
const ll INF = 1e12 + 7;

struct Node{
    ll val, ind;
    ll l, r;
    Node(ll x, ll ind){
        val = x;
        this->ind = ind;
    }
    Node() {
        val = -1;
        ind = -1;
    }
};

struct LazyTree{
    vector<Node> t;
    vector<ll> lazy;
    ll maxn;

    void build(ll v, ll l, ll r) {
        if(v > 4*maxn) return;
        t[v].l = l;
        t[v].r = r;

        ll mid = (l+r)/2;

        build(v*2, l, mid);
        build(v*2+1, mid+1, r);
    }

    LazyTree(ll n) : maxn(n) {
        for(ll i = 0; i <= 4*maxn; i++) {
            t.push_back(Node(0, i));
        }
        lazy.resize(4*n+1, 0);
        build(1, 1, n);
    }

    void push(ll ind) {
        t[ind*2].val += lazy[ind];
        lazy[ind*2] += lazy[ind];
        t[ind*2+1].val += lazy[ind];
        lazy[ind*2+1] += lazy[ind];
        lazy[ind] = 0;
    }

    ll merge(ll a, ll b) {
        return max(a,b);
    }

    void updateNode(ll ind) {
        push(ind);
        t[ind].val = merge(t[ind*2].val, t[ind*2+1].val);   
    }

    void update(ll v, ll ql, ll qr, ll added) {
        ll vl = t[v].l, vr = t[v].r;
        
        if(ql > qr) return;
        if(vl == ql && vr == qr) {
            lazy[v] += added;
            t[v].val += added;
        }
        else {
            push(v);
            ll mid = (vl + vr) / 2;
            update(v*2, ql, min(qr, mid), added);
            update(v*2+1, max(mid+1, ql), qr, added);
            updateNode(v);
        }
    }

    ll query(ll v, ll ql, ll qr) {
        ll vl = t[v].l, vr = t[v].r;
        if(ql > qr) return 0;
        if(vl >= ql && vr <= qr) return t[v].val;
        push(v);
        ll mid = (vl + vr) / 2;

        return merge(query(v*2, ql, min(mid, qr)),
                query(v*2+1, max(mid+1, ql), qr));
    }
};

vector<ll> kozos;

int get_pos(int k){
  return (int)(lower_bound(kozos.begin(),kozos.end(), k) - kozos.begin());
}

int main() {

#ifndef ONLINE_JUDGE
   freopen("../input.txt", "r", stdin);
   freopen("../output.txt", "w", stdout);
#endif
   InTheNameOfGod;

    ll n, m;
    cin >> n >> m;


    vector<ll> a(n+1), b(m+1);

    for(ll i = 1; i <= n; i++) {
        cin >> a[i];
        kozos.push_back(a[i]);
    }
    for(ll i = 1; i <= m; i++) {
        cin >> b[i];
        kozos.push_back(b[i]);
    }

    sort(kozos.begin(), kozos.end());
    /*cout << "kozos: ";
    for(int i : kozos) cout << i << ' ';
    cout << endl;*/
    auto it = unique(kozos.begin(), kozos.end());
    kozos.resize((int)(it - kozos.begin()));

    vector<pair<vector<int>, vector<int> > > vals(kozos.size());

    for(ll i = 1; i <= n; i++) {
        a[i] = get_pos(a[i]);
        vals[a[i]].first.push_back(i);
    }
    for(ll i = 1; i <= m; i++) {
        b[i] = get_pos(b[i]);
        vals[b[i]].second.push_back(i);
    }

    LazyTree aTree = LazyTree(n+1), bTree = LazyTree(m+1);

    for(ll i = 1; i <= n; i++) {
        aTree.update(1, i, i, i);
    }

    set<ll> aSet, bSet;
    for(ll i = 1; i <= m; i++) {
        bSet.insert(i);
    }


    ll mo = 0;
    for(auto num : vals) {
        //cout << num.first << "\n";

        //cout << "b: \n";
        for(ll ind : num.second) { //b
            auto it = bSet.upper_bound(ind);
            ll end;
            if(it == bSet.end()) end = m;
            else end = (*it);

            bTree.update(1, ind, end, 1);
            bSet.erase(ind);

            //cout << ind << ": " << end << endl;
        }

        //calc
        ll aVal = aTree.query(1, 1, n);
        ll bVal = bTree.query(1, 1, m);
        mo = max(mo, aVal * bVal);

        //cout << "query: " << aVal << ", " << bVal << endl;

        //cout << "a: \n";
        for(ll ind : num.first) {//a
            auto it = aSet.lower_bound(ind);
            ll end;
            if(it == aSet.end()) end = n+1; 
            else end = (*it);

            aTree.update(1, ind, end-1, -aTree.query(1, ind, ind));
            aSet.insert(ind);

            //cout << ind << ": " << end << endl;
        }

        //cout << "\n---------\n";
    }

    cout << mo;

    return 0;
}