#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(ll i=0;i<n;i++)
#define repl(i,l,r) for(ll i=(l);i<(r);i++)
#define per(i,n) for(ll i=(n)-1;i>=0;i--)
#define perl(i,r,l) for(ll i=r-1;i>=l;i--)
#define fi first
#define se second
#define pb push_back
#define ins insert
#define pqueue(x) priority_queue<x,vector<x>,greater<x>>
#define all(x) (x).begin(),(x).end()
#define CST(x) cout<<fixed<<setprecision(x)
#define vtpl(x,y,z) vector<tuple<x,y,z>>
#define rev(x) reverse(x);
using ll=long long;
using vl=vector<ll>;
using vvl=vector<vector<ll>>;
using pl=pair<ll,ll>;
using vpl=vector<pl>;
using vvpl=vector<vpl>;
const ll MOD=1000000007;
const ll MOD9=998244353;
const int inf=1e9+10;
const ll INF=4e18;
const ll dy[9]={0,1,-1,0,1,1,-1,-1,0};
const ll dx[9]={1,0,0,-1,1,-1,1,-1,0};
template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
int main(){
    ll n,m;cin >> n >> m;
    string s,t;
    rep(i,n){
        ll a;cin >> a;
        s+='0';
        rep(_,a)s+='1';
    }
    rep(i,m){
        ll b;cin >> b;
        t+='0';rep(_,b)t+='1';
    }
    n=s.size();m=t.size();
    vvl dp(n+1,vl(m+1,INF));dp[0][0]=0;
    rep(i,n+1){
        rep(j,m+1){
            if(i<n&&j<m&&s[i]==t[j])chmin(dp[i+1][j+1],dp[i][j]);
            if(i<n&&j<m)chmin(dp[i+1][j+1],dp[i][j]+1);
            if(j<m)chmin(dp[i][j+1],dp[i][j]+1);
            if(i<n)chmin(dp[i+1][j],dp[i][j]+1);
        }
    }
    cout << dp[n][m] << endl;
}