#pragma GCC optimize("O3", "unroll-loops") // "Ofast"
#pragma GCC target("avx2", "bmi", "bmi2", "lzcnt", "popcnt")
#include <bits/stdc++.h>
//#define int long long
#define vt vector
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
#define f first
#define s second
#define dbg(x) cerr << #x << " = " << x << '\n'
#define bit(x, i) ((x) >> (i) & 1)
using namespace std;
using ll = long long;
using ld = long double;
using pii = pair<int, int>;
const int N = 1e6 + 5, mod = 1e9 + 7;
const ll inf = 1e18 + 7;
const ld eps = 1e-6;
int n, m, dp[105][105][105];
set<pii> st;
int dx[] = {-1, -1, -1, 0, 0, 1, 1, 1};
int dy[] = {-1, 0, 1, -1, 1, -1, 0, 1};
void solve () {
cin >> n >> m;
vt<pii> v(m + 1);
for (int i = 1; i <= m; i++) cin >> v[i].f;
for (int i = 1; i <= m; i++) cin >> v[i].s, st.insert(v[i]);
sort(all(v));
bool ok = 1;
for (int i = 1; i < m ; i++) {
if (v[i + 1].f - v[i].f < abs(v[i + 1].s - v[i].s)) ok = 0;
}
if (ok) cout << "1\n", exit(0);
// dp[t][i][j] = max number of buttons pressed -> time t, hand1 on pos i, hand2 on pos j
for (int t = 1; t <= 100; t++) {
for (int i = 1; i <= n; i++) {
for (int j = i + 1; j <= n; j++) {
for (int k = 0; k < 8; k++) {
int x = i + dx[k], y = j + dy[k];
dp[t][i][j] = max(dp[t][i][j], dp[t - 1][x][y]);
}
if (st.count({t, i})) dp[t][i][j]++;
if (st.count({t, j})) dp[t][i][j]++;
}
}
}
int ans = 0;
for (int t = 1; t <= 100; t++) {
for (int i = 1; i <= n; i++) {
for (int j = i + 1; j <= n; j++) ans = max(ans, dp[t][i][j]);
}
}
cout << (ans == m ? 2 : 3);
cout << '\n';
}
bool testcases = 0;
signed main() {
#ifdef ONLINE_JUDGE
freopen(".in", "r", stdin);
freopen(".out", "w", stdout);
#endif
cin.tie(0) -> sync_with_stdio(0);
int test = 1;
if (testcases) cin >> test;
for (int cs = 1; cs <= test; cs++) {
solve();
}
}
