#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N=1000000+10;
int n,arr[N],ans=-9000000000000000000,lmx[N],rmx[N],ldp[N],rdp[N];
signed main() {
    cin>>n;
    for (int i=1; i<=n; i++) {
        cin>>arr[i];
    }
    lmx[1]=ldp[1]=arr[1];
    rmx[n]=rdp[n]=arr[n];
    for (int i=2; i<=n; i++) {
        ldp[i]=max(ldp[i-1]+arr[i], arr[i]);
        lmx[i]=max(lmx[i-1], ldp[i]);
    }
    for (int i=n-1; i>0; i--) {
        rdp[i]=max(rdp[i+1]+arr[i], arr[i]);
        rmx[i]=max(rdp[i+1], rdp[i]);
    }
    for (int i=2; i<n; i++) {
        ans=max(ans, lmx[i-1]+rmx[i+1]);
    }
    cout<<ans;
}