#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#define _GLIBCXX_DEBUG
using namespace std;
using std::cout;
using std::cin;
using std::endl;
using ll=long long;
using ld=long double;
ll ILL=1167167167167167167;
const int INF=2100000000;
const ll mod=998244353;
#define rep(i,a) for (ll i=0;i<a;i++)
template<class T> using _pq = priority_queue<T, vector<T>, greater<T>>;
template<class T> ll LB(vector<T> &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> ll UB(vector<T> &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> bool chmin(T &a,const T &b){if(a>b){a=b;return 1;}else return 0;}
template<class T> bool chmax(T &a,const T &b){if(a<b){a=b;return 1;}else return 0;}
template<class T> void So(vector<T> &v) {sort(v.begin(),v.end());}
template<class T> void Sore(vector<T> &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});}
void yneos(bool a){if(a) cout<<"Yes\n"; else cout<<"No\n";}


void solve();


//  rainy ~ 雨に打たれて ~
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	
	int t=1;
	//cin>>t;
	rep(i,t) solve();
}

void solve(){
	int n,m;
	cin>>n>>m;
	string S,T;
	rep(i,n){
		S+='a';
		int a;
		cin>>a;
		rep(j,a) S+='b';
	}
	rep(i,m){
		T+='a';
		int a;
		cin>>a;
		rep(j,a) T+='b';
	}
	int A=S.size(),B=T.size();
	vector<vector<int>> dp(A+1,vector<int>(B+1,-1));
	rep(i,A+1) dp[i][0]=0;
	rep(j,B+1) dp[0][j]=0;
	rep(i,A) rep(j,B){
		if(S[i]==T[j]){
			dp[i+1][j+1]=dp[i][j]+2;
		}else{
			dp[i+1][j+1]=max(dp[i][j]+1,max(dp[i][j+1],dp[i+1][j]));
		}
	}
	cout<<A+B-dp[A][B]<<"\n";
}