#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for(int i=0;i<(n);i++)
#define Inf 1000000001

string get(vector<int> a){
	string ret = "1";
	rep(i,a.size()){
		rep(j,a[i])ret += '0';
		ret += '1';
	}
	return ret;
}

int main(){
	
	int n,m;
	cin>>n>>m;
	
	vector<int> a(n),b(m);
	rep(i,n)cin>>a[i];
	rep(i,m)cin>>b[i];
	
	string s = get(a);
	string t = get(b);
	n = s.size(),m = t.size();
	vector dp(n+1,vector<int>(m+1,Inf));
	dp[0][0] = 0;
	
	rep(i,n+1){
		rep(j,m+1){
			if(i!=n){
				dp[i+1][j] = min(dp[i+1][j],dp[i][j]+1);
			}
			if(j!=m){
				dp[i][j+1] = min(dp[i][j+1],dp[i][j]+1);
			}
			if(i!=n&&j!=m){
				if(s[i]==t[j]){
					dp[i+1][j+1] = min(dp[i+1][j+1],dp[i][j]);
				}
				else{
					dp[i+1][j+1] = min(dp[i+1][j+1],dp[i][j]+1);
				}
			}
		}
	}
	cout<<dp[n][m]<<endl;
	
	return 0;
}