#include<bits/stdc++.h>
#include <iostream>
#include <numeric>
#define ull  unsigned long long
#define ll long long
#define mpa make_pair
#define pb push_back
#define ff first
#define dd float
#define trace(x) cerr << #x << " : " << x << endl
#define ss second
#define boost ios_base::sync_with_stdio(0)
#define forp(i,a,b) for(ll i=a;i<=b;i++)
#define rep(i,n)    for(ll i=0;i<n;++i)
#define ren(i,n)    for(ll i=n-1;i>=0;i--)
#define forn(i,a,b) for(ll i=a;i>=b;i--)
#define fre     freopen("input.txt","r",stdin),freopen("output.txt","w",stdout)
#define all(c) (c).begin(),(c).end()
#define tr(c,i) for(typeof((c).begin()) i = (c).begin(); i != (c).end();
#define sc(x) scanf("%lld",&x)
#define clr(x,val) memset(x,val,sizeof(x))
#define pr(x) printf("%lld\n",x) 
#define gc getchar
#define pdd pair<dd,dd>
#define prec(x) cout<<fixed<<setprecision(x)
using namespace std;
template<class T> inline void umax(T &a,T b) {
	if(a<b) a = b ;
}
template<class T> inline void umin(T &a,T b) {
	if(a>b) a = b ;
}
template<class T> inline T abs(T a) {
	return a>0 ? a : -a;
}
template<class T> inline T gcd(T a,T b) {
	return __gcd(a, b);
}
template<class T> inline T lcm(T a,T b) {
	return a/gcd(a,b)*b;
}
ll modpow(ll a,ll n,ll temp) {
	ll res=1,y=a;
	while(n>0) {
		if(n&1)res=(res*y)%temp;
		y=(y*y)%temp;
		n/=2;
	}
	return res%temp;
}
ll p2(ll n){
	return (1ll<<n);
}
ll getbit(ll j,ll i){
	return ((i>>(j-1ll))&1ll);
}
//ll a[100005],n,dp[1000005]={0},b[1000005],c[100005],dp1[1000005],bit[100005];
//ll vis[100005];
//vector<ll> adj[100005];
 
#define sz(x) x.size()
ll ison(ll mask,ll pos) {
	return (mask&(1<<pos));
}
typedef vector<ll> vi;
typedef vector<vi> vvi;
typedef pair<ll, ll> pii;
ll cbit(ll n) {
	ll k=0;
	while(n) n&=(n-1),k++;
	return k;
}
ll nbit(ll n) {
	ll k=0;
	while(n) n/=2,k++;
	return k;
}
ll mod=1e9+7;
int sgn(ll x) {
	return x < 0 ? -1 : !!x;
}
const double eps = 1e-7;
const double pi = acos(-1.0);
inline void inc(ll &x, ll y){
	x+=y;
	if(x>=mod)x-=mod;
}
inline void dec(ll &x, ll y){
	x-=y;
	if(x<0) x+=mod;
}
inline void chmax(ll &x,ll y){
	if(y>x) x=y;
}
 
inline void mulm(ll &x,ll y){
	x*=y;
	if(x>=mod) x-=mod;
}
 
//pair<ll,ll> a[1000005];
/*
void upd(ll ind,ll val){
    if(ind==0) return;
    while(ind<=n){
        bit[ind]+=val;
        ind+=(ind&-ind);
    }
}
ll qu(ll ind){
  ll k=0; while(ind>0){
    k+=bit[ind];
    ind-=(ind&-ind);
  }
    return k;
}*/
 
 
//ll tree[500005];
 
//vector<ll,pair<ll,ll> > b;
//vector<ll> adj[100005];
 
/*Tarjan incomplette
void dfs(ll s){
	vis[s]=1;
	for(ll i=0;i<adj[s].size();i++) if(!vis[adj[s][i]]) dfs(adj[s][i]);
    ofvs.pb(s);
}
void dfs2(ll s){
	vis[s]=1;
	if(wt[s]<optc){optn=0,optc=wt[s];}
	if(optc==wt[s]) optn++;
	for(ll i=0;i<rdj[s].size();i++) if(!vis[rdj[s][i]]) dfs2(rdj[s][i]);
}
*/
//typedef pair<ll,pair<ll,ll> >ver;
//string s;
/*ll tree[200005];
ll a[100005];
void build(ll node,ll ss,ll se)
{
	if(ss==se) tree[node]=a[ss];
	else
	{
		ll mid=(ss+se)/2;
		build(2*node,ss,mid);
		build(2*node+1,mid+1,se);
        tree[node]=tree[2*node]&tree[2*node+1];
	}
}*/
/*void upd(ll node,ll ss,ll se,ll idx,ll val)
{
	if(ss==se)
	a[idx]=val,tree[node]=a[idx];
	else
	{
		ll mid=(ss+se)/2;
		if(ss<=idx && idx<=mid)
		upd(2*node,ss,mid,idx,val);
		else
		upd(2*node+1,mid+1,se,idx,val);
	    tree[node]=tree[node*2]+tree[node*2+1];
	}
}*/
/*ll query(ll node,ll ss,ll se,ll l,ll r)
{
	if(r<ss || se<l)
	return 0;
	if(l<=ss && se<=r)
	return tree[node];
	ll mid=(ss+se)/2;
	ll q1=query(node*2,ss,mid,l,r);
	ll q2=query(node*2+1,mid+1,se,l,r);
	return q1&q2;
}*/
/*ll pow(ll n){
	ll t=1,i=1;
	while(i<=n) t*=10;
	return t;
}*/
//stack<ll> help;
//ll dp[1ll<<11];
 
//ll csum[100005],b[100005],help[100005];
//vector<ll> adj[1005];
//vector<ll> ans;
/*ll kmp[1000005];
ll zee[1000005];
void kmpm(string p){
	ll i,j,k=0,l;
	kmp[0]=0;
	j=0;
	for(i=1;i<p.size();i++){
		while(k && p[i]!=p[k]) k=kmp[k-1];
		if(p[i]==p[k]) k++;
		kmp[i]=k;
	}
}
ll isp(ll n){
	ll f=1,i;
	for(i=2;i<=sqrt(n);i++) if(!(n%i)) return 0;
	return 1;
}*/
/*vector<ll> zFunction(vector<ll> &s) {
    int n = (ll) s.size();
    vector<ll> z (n);
    for (int i=1, l=0, r=0; i<n; ++i) {
        if (i <= r)
            z[i] = min (r-i+1, z[i-l]);
        while (i+z[i] < n && s[z[i]] == s[i+z[i]])
            ++z[i];
        if (i+z[i]-1 > r)
            l = i,  r = i+z[i]-1;
    }
    return z;
}*/
//map<ll,ll> help;
/*ll chk(ll val,ll n,ll m){
	ll t=0,i;
	val--;
	for(i=1;i<=n;i++) t+=min(m,val/i);
	return t;
}*/
 
/*ll size[100005];
void init(ll n)
{for(int i=1;i<=n;i++) a[i]=i;}
ll root(ll x)
{
	while(a[x]!=x)
	{
		a[x]=a[a[x]];
		x=a[x];
	}
	return x;
}
ll u1(ll x,ll y)
{
	int p=root(x);
	int q=root(y);
	a[p]=a[q];
}
*/
/*ll tree[100005];
void update(ll idx, ll val){
	while(idx < 100005){
		tree[idx] = max(tree[idx], val);
		idx += (idx & (-idx));
	}
}
ll query(ll idx){
	ll ret = 0;
	while(idx > 0){
		ret = max(ret, tree[idx]);
		idx -= (idx & (-idx));
	}
	return ret;
}*/
//pair<char ,pair<ll,ll> >p[5005];[10004]
/*
//(topsort)
vector<ll> adj[100005];
vector<ll> fino;
ll vis[100005];
void dfs(ll v){
vis[v]=1;
for(ll i=0;i<adj[v].size();i++) if(!vis[adj[v][i]])dfs(adj[v][i]);
fino.pb(v);
}
*/
 
ll xo(ll i) {
	if ((i&3)==0) return i;
	if ((i&3)==1) return 1;
	if ((i&3)==2) return i+1;
	return 0;
}
//pair<ll,ll> p[10005];
/*ll a[100005];
ll bit[100005];
ll lmr[1000005];
ll pi[1000005];
ll ans[1000005];
void upd(ll ind,ll val){
    if(ind==0) return;
    while(ind<=n){
        bit[ind]+=val;
        ind+=(ind&-ind);
    }
}
ll qu(ll ind){
  ll k=0; while(ind>0){
    k+=bit[ind];
    ind-=(ind&-ind);
  }
    return k;
}
pair<pair<ll,ll>,ll> >query[1000005];
*/
 
 
 
//pair<ll,ll> a[1000005];
/*
void upd(ll ind,ll val){
    if(ind==0) return;
    while(ind<=n){
        bit[ind]+=val;
        ind+=(ind&-ind);
    }
}
ll qu(ll ind){
  ll k=0; while(ind>0){
    k+=bit[ind];
    ind-=(ind&-ind);
  }
    return k;
}*/
 
 
//ll tree[500005];
 
//vector<ll,pair<ll,ll> > b;
//vector<ll> adj[100005];
 
/*Tarjan incomplette
void dfs(ll s){
	vis[s]=1;
	for(ll i=0;i<adj[s].size();i++) if(!vis[adj[s][i]]) dfs(adj[s][i]);
    ofvs.pb(s);
}
void dfs2(ll s){
	vis[s]=1;
	if(wt[s]<optc){optn=0,optc=wt[s];}
	if(optc==wt[s]) optn++;
	for(ll i=0;i<rdj[s].size();i++) if(!vis[rdj[s][i]]) dfs2(rdj[s][i]);
}
*/
//typedef pair<ll,pair<ll,ll> >ver;
//string s;
/*ll tree[200005];
ll a[100005];
void build(ll node,ll ss,ll se)
{
	if(ss==se) tree[node]=a[ss];
	else
	{
		ll mid=(ss+se)/2;
		build(2*node,ss,mid);
		build(2*node+1,mid+1,se);
        tree[node]=tree[2*node]&tree[2*node+1];
	}
}*/
/*void upd(ll node,ll ss,ll se,ll idx,ll val)
{
	if(ss==se)
	a[idx]=val,tree[node]=a[idx];
	else
	{
		ll mid=(ss+se)/2;
		if(ss<=idx && idx<=mid)
		upd(2*node,ss,mid,idx,val);
		else
		upd(2*node+1,mid+1,se,idx,val);
	    tree[node]=tree[node*2]+tree[node*2+1];
	}
}*/
/*ll query(ll node,ll ss,ll se,ll l,ll r)
{
	if(r<ss || se<l)
	return 0;
	if(l<=ss && se<=r)
	return tree[node];
	ll mid=(ss+se)/2;
	ll q1=query(node*2,ss,mid,l,r);
	ll q2=query(node*2+1,mid+1,se,l,r);
	return q1&q2;
}*/
/*void update(ll node,ll s,ll e,ll idx,ll val){
	if(s==e){
		tree[node]=val;
		return;
	}
	else{
		ll mid=(s+e)/2;
		if(s<=idx && idx<=mid) update(node*2,s,mid,idx,val);
		else update(node*2+1,mid+1,e,idx,val);
		tree[node]=max(tree[2*node],tree[2*node+1]);
		return ;
	}
}*/
/*ll pow(ll n){
	ll t=1,i=1;
	while(i<=n) t*=10;
	return t;
}*/
//stack<ll> help;
//ll dp[1ll<<11];
 
//ll csum[100005],b[100005],help[100005];
//vector<ll> adj[1005];
//vector<ll> ans;
/*ll kmp[1000005];
ll zee[1000005];
void kmpm(string p){
	ll i,j,k=0,l;
	kmp[0]=0;
	j=0;
	for(i=1;i<p.size();i++){
		while(k && p[i]!=p[k]) k=kmp[k-1];
		if(p[i]==p[k]) k++;
		kmp[i]=k;
	}
}
ll isp(ll n){
	ll f=1,i;
	for(i=2;i<=sqrt(n);i++) if(!(n%i)) return 0;
	return 1;
}*/
/*vector<ll> zFunction(vector<ll> &s) {
    int n = (ll) s.size();
    vector<ll> z (n);
    for (int i=1, l=0, r=0; i<n; ++i) {
        if (i <= r)
            z[i] = min (r-i+1, z[i-l]);
        while (i+z[i] < n && s[z[i]] == s[i+z[i]])
            ++z[i];
        if (i+z[i]-1 > r)
            l = i,  r = i+z[i]-1;
    }
    return z;
}*/
//map<ll,ll> help;
/*ll chk(ll val,ll n,ll m){
	ll t=0,i;
	val--;
	for(i=1;i<=n;i++) t+=min(m,val/i);
	return t;
}*/
 
/*ll size[100005];
void init(ll n)
{for(int i=1;i<=n;i++) a[i]=i;}
ll root(ll x)
{
	while(a[x]!=x)
	{
		a[x]=a[a[x]];
		x=a[x];
	}
	return x;
}
ll u1(ll x,ll y)
{
	int p=root(x);
	int q=root(y);
	a[p]=a[q];
}
*/
/*ll tree[100005];
void update(ll idx, ll val){
	while(idx < 100005){
		tree[idx] = max(tree[idx], val);
		idx += (idx & (-idx));
	}
}
ll query(ll idx){
	ll ret = 0;
	while(idx > 0){
		ret = max(ret, tree[idx]);
		idx -= (idx & (-idx));
	}
	return ret;
}*/
//pair<char ,pair<ll,ll> >p[5005];[10004]
/*
//(topsort)
vector<ll> adj[100005];
vector<ll> fino;
ll vis[100005];
void dfs(ll v){
vis[v]=1;
for(ll i=0;i<adj[v].size();i++) if(!vis[adj[v][i]])dfs(adj[v][i]);
fino.pb(v);
}
*/
/*ll anc[20][100005];
ll d[100005];
vector<ll> adj[100005];
void dfs(ll v,ll p){
    for(ll i=0;i<adj[v].size();i++){
        if(adj[v][i]!=p){
            d[adj[v][i]]=d[v]+1;
            anc[0][adj[v][i]]=v;
            dfs(adj[v][i],v);
        }
    }
}
 
ll lca(ll a,ll b){
    if(d[a]>d[b])swap(a,b);
    ll diff=d[b]-d[a];
    for(ll i=0;i<20;i++)if(diff&(1<<i))b=anc[i][b];
    for(ll i=19;i>=0;i--){
        if(anc[i][a]!=anc[i][b]) a=anc[i][a],b=anc[i][b];
    }
    if(a==b)return a;
    return anc[0][a];
}
ll dist(ll a,ll b){
    ll l=lca(a,b);
    return d[a]+d[b]-2*d[l];
}*/
//pair<ll,ll> p[10005];
/*ll a[100005];
ll bit[100005];
ll lmr[1000005];
ll pi[1000005];
ll ans[1000005];
void upd(ll ind,ll val){
    if(ind==0) return;
    while(ind<=n){
        bit[ind]+=val;
        ind+=(ind&-ind);
    }
}
ll qu(ll ind){
  ll k=0; while(ind>0){
    k+=bit[ind];
    ind-=(ind&-ind);
  }
    return k;
}
pair<pair<ll,ll>,ll> >query[1000005];
*/
 
 
//pair<ll,ll> a[205];
//template for #trie
//vector<ll> adj[100005],adjr[100005];
//ll a[100005],dp[100005];
/*
ll block;
ll gb(ll pos) {
	return (pos-1)/block;
}
bool comp(pair<pii,ll> a, pair<pii,ll> b){
    ll b1 = gb(a.ff.ff);
    ll b2 = gb(b.ff.ss);
    if(b1 != b2)   return b1 < b2;
    return a.ss < b.ss;
}*/
#define nmax 111111
#define bmax 1111111
//////
ll a[1005],b[1005];
int main(){
	ll x,m,n,k,s,t,j;
	boost;
	cin>>n;
	for(ll i=1;i<=n;i++)cin>>a[i],a[i]+=a[i-1];
	for(ll i=1;i<=n;i++)cin>>b[i];
	for(ll i=n;i>=1;i--)b[i]+=b[i+1];
	ll ans=0;
	for(ll i=1;i<=n;i++)ans=max(ans,a[i]+b[i]);
	cout<<ans;
}   

Measured memory_bytes: 256