#include <bits/stdc++.h>

using i64 = long long;
using u64 = unsigned long long;
using u32 = unsigned;

constexpr i64 inf = 1E18;

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    
    int n;
    std::cin >> n;
    
    std::vector<int> a(n);
    for (int i = 0; i < n; i++) {
        std::cin >> a[i];
    }
    
    std::array<i64, 2> dp {-inf, -inf};
    i64 ans = 0;
    for (int i = 0; i < n; i++) {
        ans = std::max({ans, dp[0], dp[1] + a[i]});
        dp = {
            std::max({dp[0], dp[0] + a[i], dp[1] + 2 * a[i], i64(a[i])}),
            std::max({dp[1], dp[0], dp[1] + a[i], 0LL})
        };
    }
    std::cout << ans << "\n";
    
    return 0;
}