#include<iostream>
#include<array>
#include<string>
#include<cstdio>
#include<vector>
#include<cmath>
#include<algorithm>
#include<functional>
#include<iomanip>
#include<queue>
#include<ciso646>
#include<random>
#include<map>
#include<set>
#include<complex>
#include<bitset>
#include<stack>
#include<unordered_map>
#include<utility>
#include<tuple>
#include<cassert>
using namespace std;
typedef long long ll;
const ll mod = 1000000007;
const ll INF = (ll)1000000007 * 1000000007;
typedef pair<int, int> P;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define Per(i,sta,n) for(int i=n-1;i>=sta;i--)
typedef long double ld;
const ld eps = 1e-8;
const ld pi = acos(-1.0);
typedef pair<ll, ll> LP;
int dx[4]={1,-1,0,0};
int dy[4]={0,0,1,-1};
template<class T>bool chmax(T &a, const T &b) {if(a<b){a=b;return 1;}return 0;}
template<class T>bool chmin(T &a, const T &b) {if(b<a){a=b;return 1;}return 0;}

int n,m;
int a[2010],b[2010];
int dp[5010][5010];
vector<int> c,d;

void solve(){
    cin >> n >> m;
    rep(i,n) {
        cin >> a[i];
        c.push_back(0);
        rep(j,a[i]) c.push_back(1);
    }
    rep(i,m) {
        cin >> b[i];
        d.push_back(0);
        rep(j,b[i]) d.push_back(1);
    }
    int S=c.size(),T=d.size();
    // rep(i,S) cout << c[i] << " ";
    // cout << "" << endl;
    // rep(i,T) cout << d[i] << " ";
    // cout << "" << endl;
    rep(i,S+1) dp[i][0]=i;
    rep(i,T+1) dp[0][i]=i;
    Rep(i,1,S+1){
        Rep(j,1,T+1){
            dp[i][j]=min(dp[i-1][j],dp[i][j-1])+1;
            chmin(dp[i][j],dp[i-1][j-1]+(c[i-1]!=c[j-1]));
            //cout << i << " " << j << " " << dp[i][j] << endl;
        }
    }
    cout << dp[S][T] << endl;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(50);
    solve();
}