#include <bits/stdc++.h>
#include <atcoder/all>

namespace neguse {}
using namespace std;
using namespace atcoder;
using namespace neguse;

typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<ld> vld;
typedef vector<vi> vvi;
typedef vector<vll> vvll;
typedef vector<string> vs;
typedef vector<pii> vpii;
typedef vector<pll> vpll;

#define _overload3(_1,_2,_3,name,...) name
#define _rep(i,n) repi(i,0,n)
#define repi(i,a,b) for(int i=int(a);i<int(b);++i)
#define rep(...) _overload3(__VA_ARGS__,repi,_rep,)(__VA_ARGS__)
#define _rrep(i,n) rrepi(i,n-1,-1)
#define rrepi(i,a,b) for(int i=int(a);i>int(b);--i)
#define rrep(...) _overload3(__VA_ARGS__,rrepi,_rrep)(__VA_ARGS__)
#define _each1(i,v) for(auto& i:v)
#define _each2(i,j,v) for(auto& [i,j]:v)
#define each(...) _overload3(__VA_ARGS__,_each2,_each1,)(__VA_ARGS__)

#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define SORT(x) sort(all(x))
#define RSORT(x) sort(rall(x))
#define REVERSE(x) reverse(all(x))

#define dump(x) cerr << #x << " = " << (x) << '\n'
#define print(x) cout << (x) << '\n'
#define yes(f) cout << ((f) ? "Yes" : "No") << '\n'

#define ge(v, x) (int)(lower_bound(all(v), x) - v.begin())
#define gt(v, x) (int)(upper_bound(all(v), x) - v.begin())
#define le(v, x) (int)(upper_bound(all(v), x) - v.begin())-1
#define lt(v, x) (int)(lower_bound(all(v), x) - v.begin())-1

template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }

ostream& operator<<(ostream& os, const modint998244353& a) { return os << a.val(); }
ostream& operator<<(ostream& os, const modint1000000007& a) { return os << a.val(); }

template<class T> istream& operator>>(istream& is, vector<T>& vec) { for (T& x : vec) is >> x; return is; }
template<class T> ostream& operator<<(ostream& os, const vector<T>& vec) { for (const T& x : vec) os << x << ' '; return os; }


using namespace neguse;

int main() {
    int N;
    cin >> N;
    vi A(N);
    cin >> A;

    bool is_dec = true;
    rep(i, N - 1) if (A[i] <= A[i + 1]) is_dec = false;
    if (is_dec) {
        cout << A[N - 1] << endl;
        return 0;
    }

    vector dp(N + 1, vector(2, vll(2, -1e18)));
    dp[0][0][0] = 0;
    rep(i, N) {
        rep(j, 2) {
            // A[i]を使う場合
            rep(k, 2) chmax(dp[i + 1][(j + 1) % 2][1], dp[i][j][k] + (j ? A[i] : -A[i]));
            // A[i]を使わない場合
            rep(k, 2) chmax(dp[i + 1][j][k], dp[i][j][k]);
        }
    }

    ll ans = 0;
    rep(i, 2) chmax(ans, dp[N][i][1]);
    cout << ans << endl;

    return 0;
}