#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define rep(i,n) for(int i=0;i<n;i++)
#define rrep(i,n) for(int i=n-1;i>=0;i--)
#define rrep2(i,n,k) for(int i=n-1;i>=n-k;i--)
#define vll(n,i) vector<long long>(n,i)
#define v2ll(n,m,i) vector<vector<long long>>(n,vll(m,i))
#define v3ll(n,m,k,i) vector<vector<vector<long long>>>(n,v2ll(m,k,i))
#define v4ll(n,m,k,l,i) vector<vector<vector<vector<long long>>>>(n,v3ll(m,k,l,i))
#define all(v) v.begin(),v.end()
#define chmin(k,m) k = min(k,m)
#define chmax(k,m) k = max(k,m)
#define Pr pair<ll,ll>
#define Tp tuple<ll,ll,ll>
#define riano_ std::ios::sync_with_stdio(false);std::cin.tie(nullptr)
using Graph = vector<vector<int>>;

const ll mod = 90007;
template<uint64_t mod>
struct modint{
    uint64_t val;
    constexpr modint(const int64_t val_=0) noexcept:val((val_%int64_t(mod)+int64_t(mod))%int64_t(mod)){}
    constexpr modint operator-() const noexcept{
        return modint(*this)=mod-val;
    }
    constexpr modint operator+(const modint rhs) const noexcept{
        return modint(*this)+=rhs;
    }
    constexpr modint operator-(const modint rhs) const noexcept{
        return modint(*this)-=rhs;
    }
    constexpr modint operator*(const modint rhs) const noexcept{
        return modint(*this)*=rhs;
    }
    constexpr modint operator/(const modint rhs) const noexcept{
        return modint(*this)/=rhs;
    }
    constexpr modint &operator+=(const modint rhs) noexcept{
        val+=rhs.val;
        val-=((val>=mod)?mod:0);
        return (*this);
    }
    constexpr modint &operator-=(const modint rhs) noexcept{
        val+=((val<rhs.val)?mod:0);
        val-=rhs.val;
        return (*this);
    }
    constexpr modint &operator*=(const modint rhs) noexcept{
        val=val*rhs.val%mod;
        return (*this);
    }
    constexpr modint &operator/=(modint rhs) noexcept{
        uint64_t ex=mod-2;
        modint now=1;
        while(ex){
            now*=((ex&1)?rhs:1);
            rhs*=rhs,ex>>=1;
        }
        return (*this)*=now;
    }
    modint & operator++(){
        val++;
        if (val == mod) val = 0;
        return *this;
    }
    modint operator++(int){
        modint<mod> res = *this;
        ++*this;
        return res;
    }
    constexpr bool operator==(const modint rhs) noexcept{
        return val==rhs.val;
    }
    constexpr bool operator!=(const modint rhs) noexcept{
        return val!=rhs.val;
    }
    friend constexpr ostream &operator<<(ostream& os,const modint x) noexcept{
        return os<<(x.val);
    }
    friend constexpr istream &operator>>(istream& is,modint& x) noexcept{
        uint64_t t;
        is>>t,x=t;
        return is;
    }
};
typedef modint<mod> mint;
mint pw(long long a,long long b,long long m = mod){
    if(a%m==0) return mint(0);
    if(b==0) return mint(1);
    else if(b%2==0){
        long long x = pw(a,b/2,m).val;
        return mint(x*x);
    }
    else{
        long long x = pw(a,b-1,m).val;
        return mint(a*x);
    }
}
mint modinv(long long a, long long m = mod) {
    long long b = m, u = 1, v = 0;
    while (b) {
        long long t = a / b;
        a -= t * b; swap(a, b);
        u -= t * v; swap(u, v);
    }
    u %= m;
    return mint(u);
}
#define vm(n,i) vector<mint>(n,i)
#define v2m(n,m,i) vector<vector<mint>>(n,vm(m,i))
#define v3m(n,m,k,i) vector<vector<vector<mint>>>(n,v2m(m,k,i))
#define v4m(n,m,k,l,i) vector<vector<vector<vector<mint>>>>(n,v3m(m,k,l,i))

int main() {
    riano_; ll ans = 0;
	ll N,M; cin >> N >> M;
    ll a[N],b[M];
    rep(i,N) cin >> a[i];
    rep(i,M) cin >> b[i];
    set<ll> as,bs;
    rep(i,N-1){
        as.insert(a[i]);
        a[i+1] += a[i]; 
    }
    rep(i,M-1){
        bs.insert(b[i]);
        b[i+1] += b[i];
    }
    if(a[N-1]==0){
        cout << b[M-1]+M-1 << endl; return 0;
    }
    if(b[M-1]==0){
        cout << a[N-1]+N-1 << endl; return 0;
    }
    //cout << a[N-1] << " " << b[M-1] << endl;
    auto dp = v2ll(a[N-1]+2,b[M-1]+2,2e18);
    dp[0][0] = 0;
    ll id1 = 0,id2 = 0;
    bool aa[a[N-1]+1],bb[b[M-1]+1];
    rep(i,a[N-1]){
        if(as.count(i+1)) aa[i+1] = true;
        else aa[i+1] = false;
    }
    rep(i,b[M-1]){
        if(bs.count(i+1)) bb[i+1] = true;
        else bb[i+1] = false;
    }
    rep(i,a[N-1]){
        rep(j,b[M-1]){
            if(aa[i+1]&&bb[j+1]) chmin(dp[i+1][j+1],dp[i][j]);
            if(aa[i+1]&&!bb[j+1]){
                chmin(dp[i+1][j+1],dp[i][j]+1);
                chmin(dp[i+1][j+2],dp[i][j]+1);
            }
            if(!aa[i+1]&&bb[j+1]){
                chmin(dp[i+1][j+1],dp[i][j]+1);
                chmin(dp[i+2][j+1],dp[i][j]+1);
            }
            if(!aa[i+1]&&!bb[j+1]){
                chmin(dp[i+1][j+1],dp[i][j]);
            }
            if(!aa[i+1]){
                chmin(dp[i+1][j],dp[i][j]+1);
            }
            else{
                chmin(dp[i+1][j],dp[i][j]+2);
            }
            if(!bb[j+1]){
                chmin(dp[i][j+1],dp[i][j]+1);
            }
            else{
                chmin(dp[i][j+1],dp[i][j]+2);
            }
        }
    }
    ans = dp[a[N-1]][b[M-1]];
    cout << ans << endl;
}