1

// 题目链接  http://codeforces.com/contest/1006/problem/C
#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
#include <algorithm>
#include <utility>
#include <vector>
#include <map>
#include <queue>
#include <stack>
#include <cstdlib>
#include <deque>
#include <set>
typedef long long ll;
#define lowbit(x) (x&(-x))
#define ls l,m,rt<<1
#define rs m+1,r,rt<<1|1
using namespace std;
map<ll,ll>mp;
map<ll,int>id;
int n;
const int N=2e5+9;
ll a[N];
ll sum1[N],sum2[N];
int main()
{  //cout<<"njjni
";
    scanf("%d",&n);
    sum1[0]=0;
    ll sum=0;
    for(int i=1;i<=n;i++){
        scanf("%lld",&a[i]);
        sum+=a[i];
        sum1[i]=sum1[i-1]+a[i];
        mp[sum1[i]]=1;
        id[sum1[i]]=i;
    }
    /*    
    if(sum%2==0){
        printf("%lld
",sum/2);
        return  0;
    }
    //上面的是错误的，例如 ：
    1 1
    2
    就应该输出0
    */
    sum2[n]=a[n];
    for(int i=n-1;i>=1;i--){
        sum2[i]=sum2[i+1]+a[i];
        
    }
    ll maxx=0;
    int i;
    for(int j=n;j>=1;j--){      
        if(mp[sum2[j]]==1){
            i=id[sum2[j]];
            if(i<j){
                //cout<<i<<" "<<j<<endl;
            maxx=max(maxx,sum2[j]);
            }
        }
    }
    printf("%lld
",maxx);
    return 0;
}