#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic pop
using namespace std;
using namespace atcoder;
#define rep(i,n)for (int i = 0; i < int(n); ++i)
#define rrep(i,n)for (int i = int(n)-1; i >= 0; --i)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
template<class T> void chmax(T& a, const T& b) { a = max(a, b); }
template<class T> void chmin(T& a, const T& b) { a = min(a, b); }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n, m;
  cin >> n >> m;
  vector<char> a, b;
  rep(_, 2) {
    rep(i, n) {
      int x;
      cin >> x;
      rep(_, x) a.emplace_back(0);
      if (i != n - 1) a.emplace_back(1);
    }
    n = a.size();
    swap(n, m);
    swap(a, b);
  }
  constexpr int INF = 1001001001;
  VVI dp(n + 1, VI(m + 1, INF));
  dp[0][0] = 0;
  rep(i, n + 1) rep(j, m + 1) {
    if (i < n) chmin(dp[i + 1][j], dp[i][j] + 1);
    if (j < m) chmin(dp[i][j + 1], dp[i][j] + 1);
    if (i < n && j < m) chmin(dp[i + 1][j + 1], dp[i][j] + (a[i] != b[j]));
  }
  cout << dp[n][m] << '\n';
}