#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int INF = 1e9 + 10;
const ll INFL = 4e18;

int main() {
    int N;
    cin >> N;
    vector<ll> A(N);
    for (int i = 0; i < N; i++) cin >> A[i];

    vector<vector<vector<ll>>> dp(N + 1, vector<vector<ll>>(2, vector<ll>(2, -INFL)));
    dp[0][0][0] = 0;

    for (int i = 0; i < N; i++) {
        for (int j = 0; j < 2; j++) {
            for (int k = 0; k < 2; k++) {
                dp[i + 1][j][k] = max(dp[i][j][k], dp[i + 1][j][k]);
                ll& n = dp[i + 1][min(j + 1, 1)][1 - k % 2];
                n = max(n, dp[i][j][k] + (k == 0 ? -1ll : 1ll) * A[i]);
            }
        }
    }

    cout << max(dp[N][1][0], dp[N][1][1]) << endl;
}