#include <bits/stdc++.h>
using namespace std;
template <class T> 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);
	if(N>5000) {
		cout << -1 << endl;
		return 0;
	}
	//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 i = 1; i <= N; ++i) {
		for(int j = 0; j+i <= N; j+=i) range.push_back({j,j+i-1});
		for(int j = N; 0 <= j-i; j-=i) range.push_back({j-i,j-1});
	}
	
	//Mo順ソート　O(N*logN*log(NlogN))
	int bucket = sqrt(N);
	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++;
		}
		//左端を狭める
		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();
	}

	long long ans = 0;
	int cnt = 0;
	//区間長決め打ち全探索O(N*logN)
	for(long long i = 1; i <= N; ++i) {
		int M = N/i;
		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 j = 0;    j < M; ++j) lRange[j] = range[cnt+j];
		for(int j = M-1; 0 <= j; --j) rRange[j] = range[cnt + 2*M-1 - j];
		//中央値取得
		for(int j = 0;    j < M; ++j) lSum[j]   = i*mp[lRange[j].first*N+lRange[j].second];
		for(int j = M-1; 0 <= j; --j) rSum[j]   = i*mp[rRange[j].first*N+rRange[j].second];
		//累積和
		for(int j = 1;    j < M; ++j) lSum[j]  += lSum[j-1];
		for(int j = M-2; 0 <= j; --j) rSum[j]  += rSum[j+1];
		//累積max
		for(int j = 1;    j < M; ++j) chmax(lSum[j],lSum[j-1]);
		for(int j = M-2; 0 <= j; --j) chmax(rSum[j],rSum[j+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 k = 0;
		for(int j = 0; j < M; ++j) {
			while(k < M && range[cnt + j].second >= range[cnt + 2*M-1-k].first) k++;
			if(k<M && lRange[j].second < rRange[k].first) {
				chmax(ans,lSum[j]+rSum[k]);
			}
		}
		cnt += 2*M;
	}
	cout << ans << endl;
    return 0;
}