#include<bits/stdc++.h>

using namespace std;

#define N 30000

int a[N],b[N],f[N],sa[N];

int main(){
    ios::sync_with_stdio(0); cin.tie(0);
    int n; cin>>n;   
    for (int i=1;i<=n;++i){
        cin>>a[i];
        sa[i]=sa[i-1]+a[i];
    }
    for (int i=1;i<=n;++i){
        cin>>b[i];
    }
    int mx=sa[n]+n*10;
    int l=b[1]+sa[n],r=mx;
    int ans=0;
    auto check=[&](int k){
        f[0]=k+1; f[1]=b[1];
        f[n]=k+1;
        for (int i=2;i<=n;++i){
            f[i]=min(f[i-1],f[i-2])+b[i];
            if (f[i]+sa[n]-sa[i-1]>k) f[i]=k+1;
            if (f[i]==k+1&&f[i-1]==k+1) return 0;
        }
        return int(f[n]<=k);
    };
    while (l<=r){
        int mid=(l+r)>>1;
        if (check(mid)){
            ans=mid; r=mid-1;
        }
        else{
            l=mid+1;
        }
    }
    assert(ans>0);
    cout<<ans<<'\n';
}