#include "bits/stdc++.h"
using namespace std;
#ifdef duc_debug
#include "bits/debug.h"
#else
#define debug(...)
#endif
const int maxn = 5e5 + 5;
int n, m;
int a[maxn], t[maxn];
int ord[maxn];
void solve() {
cin >> n >> m;
for(int i = 1; i <= m; ++i) {
cin >> t[i];
}
for(int i = 1; i <= m; ++i) {
cin >> a[i];
ord[i] = i;
}
// rotate 45 ccw
// MIS on dag
sort(ord + 1, ord + m + 1, [](const int &x, const int &y) -> bool {
if(t[x] - a[x] != t[y] - a[y]) return t[x] - a[x] > t[y] - a[y];
return t[x] + a[x] > t[y] + a[y];
});
vector<int> vec;
for(int i = 1; i <= m; ++i) {
auto it = lower_bound(vec.begin(), vec.end(), t[ord[i]] + a[ord[i]]);
if(it == vec.end()) vec.push_back(t[ord[i]] + a[ord[i]]);
else *it = t[ord[i]] + a[ord[i]];
}
cout << (int)vec.size();
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
solve();
return 0;
}
