#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
using ll = long long;
constexpr int INF = 0x3f3f3f3f;
constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr double EPS = 1e-8;
constexpr int MOD = 1000000007;
// constexpr int MOD = 998244353;
constexpr int DY[]{1, 0, -1, 0}, DX[]{0, -1, 0, 1};
constexpr int DY8[]{1, 1, 0, -1, -1, -1, 0, 1}, DX8[]{0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U> inline bool chmax(T& a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U> inline bool chmin(T& a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    std::cin.tie(nullptr);
    std::ios_base::sync_with_stdio(false);
    std::cout << fixed << setprecision(20);
  }
} iosetup;

template <typename T>
int levenshtein_distance(const T &a, const T &b) {
  int n = a.size(), m = b.size();
  std::vector<std::vector<int>> dp(n + 1, std::vector<int>(m + 1));
  for (int i = 1; i <= n; ++i) dp[i][0] = i;
  std::iota(dp[0].begin(), dp[0].end(), 0);
  for (int i = 1; i <= n; ++i) for (int j = 1; j <= m; ++j) {
    dp[i][j] = std::min({dp[i - 1][j] + 1, dp[i][j - 1] + 1, dp[i - 1][j - 1] + (a[i - 1] != b[j - 1])});
  }
  return dp[n][m];
}

int main() {
  int n, m; cin >> n >> m;
  string a = "", b = "";
  REP(i, n) {
    int ai; cin >> ai;
    while (ai--) a += '1';
    if (i + 1 < n) a += '0';
  }
  REP(i, m) {
    int bi; cin >> bi;
    while (bi--) b += '1';
    if (i + 1 < m) b += '0';
  }
  cout << levenshtein_distance(a, b) << '\n';
  return 0;
}