#include <bits/stdc++.h>
using namespace std;
#define gc getchar_unlocked
#define fo(i, n) for (int i = 0; i < n; i++)
#define rfo(i, n) for (int i = n - 1; i >= 0; i--)
#define REP(i, a, b) for (int i = a; i < b; i++)
#define RREP(i, a, b) for (int i = a; i >= b; i--)
#define ll long long
#define si(x) scanf("%d", &x)
#define sl(x) scanf("%lld", &x)
#define ss(s) scanf("%s", s)
#define pi(x) printf("%d\n", x)
#define pl(x) printf("%lld\n", x)
#define ps(s) printf("%s\n", s)
#define deb(x) cout << #x << "=" << x << endl
#define deb2(x, y) cout << #x << "=" << x << "," << #y << "=" << y << endl
#define deb3(x, y, z) cout << #x << "=" << x << "," << #y << "=" << y << "," << #z << "=" << z << endl
#define pb push_back
#define mp make_pair
#define F first
#define S second
#define all(x) x.begin(), x.end()
#define clr(x) memset(x, 0, sizeof(x))
#define sortall(x) sort(all(x))
#define tr(it, a) for (auto it = a.begin(); it != a.end(); it++)
#define PI 3.1415926535897932384626
typedef pair<int, int> pii;
typedef pair<ll, ll> pl;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<pii> vpii;
typedef vector<pl> vpl;
typedef vector<vi> vvi;
typedef vector<vl> vvl;
int mpow(int base, int exp);
const int mod = 1'000'000'007;
const int N = 15e3 + 100, M = N;
vi g[N];
int vis[N];
stack<int> st;
void dfs(int cur)
{
if (vis[cur])
return;
for (auto e : g[cur])
dfs(e);
st.push(cur);
}
void solve()
{
int n, m;
cin >> n >> m;
vpii times(m);
fo(i, m) cin >> times[i].F;
fo(i, m) cin >> times[i].S;
sortall(times);
times.resize(distance(times.begin(), unique(all(times))));
fo(i, m)
{
fo(j, m)
{
if (times[j].F > times[i].F && times[j].S > times[i].S)
{
g[i].pb(j);
}
}
}
fo(i, m)
{
if (vis[i])
continue;
dfs(i);
}
vi dp(m);
int ans = 0;
while (st.size())
{
int cur = st.top();
st.pop();
for (auto e : g[cur])
{
dp[e] = max(dp[e], dp[cur] + 1);
}
}
fo(i, m) ans = max(ans, dp[i]);
cout << ans << '\n';
return;
}
int main()
{
ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
srand(chrono::high_resolution_clock::now().time_since_epoch().count());
int t = 1;
int cs = 0;
while (t - cs)
{
solve();
cs++;
}
return 0;
}
int mpow(int base, int exp)
{
base %= mod;
int result = 1;
while (exp > 0)
{
if (exp & 1)
result = ((ll)result * base) % mod;
base = ((ll)base * base) % mod;
exp >>= 1;
}
return result;
}
