#include <bits/stdc++.h>
using namespace std;
#define bokusunny ios::sync_with_stdio(false), cin.tie(nullptr);

void solve() {
  int N, M;
  cin >> N >> M;
  vector<int> A(N);
  for (int i = 0; i < N; i++) cin >> A[i];
  vector<int> B(M);
  for (int i = 0; i < M; i++) cin >> B[i];

  vector<int> AA;
  for (auto &a : A) {
    AA.push_back(0);
    for (int i = 0; i < a; i++) AA.push_back(1);
  }
  vector<int> BB;
  for (auto &b : B) {
    BB.push_back(0);
    for (int i = 0; i < b; i++) BB.push_back(1);
  }

  const int INFINT = 1 << 30;
  int sz_a = (int)AA.size();
  int sz_b = (int)BB.size();
  vector dp(sz_a + 1, vector<int>(sz_b + 1, INFINT));
  dp[0][0] = 0;
  for (int i = 0; i <= sz_a; i++) {
    for (int j = 0; j <= sz_b; j++) {
      if (i > 0) dp[i][j] = min(dp[i][j], dp[i - 1][j] + 1);
      if (j > 0) dp[i][j] = min(dp[i][j], dp[i][j - 1] + 1);
      if (i > 0 && j > 0) {
        dp[i][j] = min(dp[i][j], dp[i - 1][j - 1] + (int)(AA[i - 1] != BB[j - 1]));
      }
    }
  }

  cout << dp[sz_a][sz_b] << endl;
}

int main() {
  bokusunny;
  solve();

  return 0;
}