#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n, m; cin >> n >> m;
	vector<int>a, b;
	rep(i, n) {
		a.push_back(0);
		int x; cin >> x;
		rep(j, x)a.push_back(1);
	}
	rep(i, m) {
		b.push_back(0);
		int x; cin >> x;
		rep(j, x)b.push_back(1);
	}
	vector<vector<int>> dp(a.size() + 1, vector<int>(b.size() + 1, INF));
	rep(i, a.size() + 1)dp[i][0] = i;
	rep(i, b.size() + 1)dp[0][i] = i;
	rep2(i, 1, a.size() + 1)rep2(j, 1, b.size() + 1) {
		if (a[i - 1] == b[j - 1])chmin(dp[i][j], dp[i - 1][j - 1]);
		else chmin(dp[i][j], dp[i - 1][j - 1] + 1);
		chmin(dp[i][j], dp[i - 1][j - 0] + 1);
		chmin(dp[i][j], dp[i - 0][j - 1] + 1);
	}
	cout << dp[a.size()][b.size()] << endl;
	return 0;
}