#include <bits/stdc++.h>
using namespace std;
template <class T> inline void chmax(T& a, const T b){a=max(a,b);}

inline void balanceLtoR(multiset<long long>& stl,multiset<long long>& str) {
	while(stl.size()>str.size()+1) {
		long long tmp = *stl.rbegin();
		str.insert(tmp);
		stl.erase(stl.find(tmp));
	}
}

inline void balanceRtoL(multiset<long long>& stl,multiset<long long>& str) {
	if(stl.size()<str.size()) {
		stl.insert(*str.begin());
		str.erase(str.begin());
	}
}

inline void exchange(multiset<long long>& stl,multiset<long long>& str){
	long long tmpl = *stl.rbegin();
	long long tmpr = *str.begin();
	if(tmpl>tmpr) {
		stl.erase(stl.find(tmpl));
		stl.insert(tmpr);
		str.erase(str.find(tmpr));
		str.insert(tmpl);
	}
}

int main() {
	cin.tie(0);ios::sync_with_stdio(false);
	int N; cin >> N;
	assert(1<=N && N <= 10000);
	vector<long long> A(N);
	for(int i = 0; i < N; ++i) cin >> A[i];
	for(int i = 0; i < N; ++i) assert(-1000000000<=A[i] && A[i] <= 1000000000);

	//クエリ区間を列挙、調和級数なのでO(N*logN)
	vector<pair<long long,long long>> range;
	for(int n = 1; n <= N; ++n) {
		int M = N/n;
		for(int i = 0;     i+n <= N; i+=n) range.push_back({i,i+n-1});
		for(int i = N-M*n; i+n <= N; i+=n) range.push_back({i,i+n-1});
	}
	
	//Mo順ソート　O(N*logN*log(NlogN))
	int bucket = max(1,(int)sqrt(N)-10);
	vector<int> idx(range.size());
	iota(idx.begin(),idx.end(),0);
	sort(idx.begin(),idx.end(),[&](int a, int b){
		auto  al = range[a].first/bucket;
		auto& ar = range[a].second;
		auto  bl = range[b].first/bucket;
		auto& br = range[b].second;
		return (al != bl) ? (al < bl) : ((al%2)?(ar > br):(ar < br));
	});



	//Moで中央値列挙　O(N*sqrt(N)*(logN)^2)
	int l = 0, r = 0;
	multiset<long long> stl,str;
	stl.insert(A[0]);
	unordered_map<long long,long long> mp;

	for(int& i:idx){
		auto& xl = range[i].first;
		auto& xr = range[i].second;
		
		//左端を広げる
		while(xl < l){
			l--;
			stl.insert(A[l]);
			if(str.size()) exchange(stl,str);
			balanceLtoR(stl,str);
		}
		//右端を広げる
		while(r < xr){
			r++;
			stl.insert(A[r]);
			if(str.size()) exchange(stl,str);
			balanceLtoR(stl,str);
		}
		//左端を狭める
		while(l < xl){
			if(stl.count(A[l])) {
				stl.erase(stl.find(A[l]));
				balanceRtoL(stl,str);
			}
			else {
				str.erase(str.find(A[l]));
				balanceLtoR(stl,str);
			}
			l++;
		}
		//右端を狭める
		while(xr < r){
			if(stl.count(A[r])) {
				stl.erase(stl.find(A[r]));
				balanceRtoL(stl,str);
			}
			else {
				str.erase(str.find(A[r]));
				balanceLtoR(stl,str);
			}
			r--;
		}
		mp[xl*N+xr] = *stl.rbegin();
	}

	cout << -1 << endl;
	return 0;

	long long ans = 0;
	int cnt = 0;
	//区間長決め打ち全探索O(N*logN)
	for(long long n = 1; n <= N; ++n) {
		int M = N/n;
		vector<long long> lSum(M,0),rSum(M,0);
		vector<pair<long long,long long>> lRange(M),rRange(M);
		//区間取得
		for(int i = 0; i < M; ++i) {
			lRange[i] = range[cnt + i];
			lSum[i]   = n*mp[lRange[i].first*N+lRange[i].second];
			rRange[i] = range[cnt + i + M];
			rSum[i]   = n*mp[rRange[i].first*N+rRange[i].second];
		}
		//累積和
		for(int i = 1;    i < M; ++i) lSum[i]  += lSum[i-1];
		for(int i = M-2; 0 <= i; --i) rSum[i]  += rSum[i+1];
		//累積max
		for(int i = 1;    i < M; ++i) chmax(lSum[i],lSum[i-1]);
		for(int i = M-2; 0 <= i; --i) chmax(rSum[i],rSum[i+1]);

		chmax(ans,lSum[M-1]);
		chmax(ans,rSum[0]);

		//尺取りしながら左右決め打ち全探索
		int j = 0;
		for(int i = 0; i < M; ++i) {
			while(j < M && lRange[i].second >= rRange[j].first) j++;
			if(j<M && lRange[i].second < rRange[j].first) {
				chmax(ans,lSum[i]+rSum[j]);
			}
		}
		cnt += 2*M;
	}
	cout << ans << endl;
    return 0;
}