// Problem :
#pragma GCC optimize("Ofast,unroll-loops,inline,fast-math")
#pragma GCC target("avx2,sse4.2,bmi,bmi2,lzcnt,popcnt,fma")
#include <bits/stdc++.h>
#if LOCAL
#include "algo/debug.h"
#endif
#define task "sol"
using namespace std;
using ll = long long;
constexpr int MOD = 1e9 + 7;
constexpr int LIMIT = 1e6 + 7;
constexpr ll INF = LLONG_MAX;
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr); cout.tie(nullptr);
if (fopen(task".inp", "r")) {
freopen(task".inp", "r", stdin), freopen(task".out", "w", stdout);
}
int n;
cin >> n;
vector<ll> dp(3, INF);
ll curr = 0, res = -INF;
for (int i = 0; i < n; ++i) {
ll val;
cin >> val;
curr += val;
if (i < 3) {
dp[i] = min(dp[i], val);
} else {
int r = i % 3;
res = max(res, curr - dp[r]);
dp[r] = min(dp[r], curr);
}
}
cout << res;
return 0;
}
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