#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];
    }
    for (int k=b[1]+sa[n];k<=n*20;++k){
        f[0]=n*21; f[1]=b[1];
        f[n]=n*21;
        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]=n*21;
            if (f[i]==n*21&&f[i-1]==n*21) break;
        }
        if (f[n]<n*21){
            cout<<k<<'\n';
            break;
        }
    }
}