#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, mm;
  cin >> n >> mm;
  map<int, int> m;
  map<int, int>::iterator it;
  int a[n + 1];
  for (int i = 1; i <= n; i++) cin >> a[i];
  while (mm--) {
    int x;
    cin >> x;
    m[x]++;
  }
  int c = 0;
  for (int i = 1; i <= n; i++) {
    it = m.lower_bound(a[i]);
    if (it == m.end()) {
      c++;
    } else {
      it->second = it->second - 1;
      if (it->second == 0) m.erase(it);
    }
  }
  cout << c << '\n';
}
