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npsc2019bb.cpp

#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#pragma GCC optimize("-O3")
#pragma GCC optimize("inline")
#pragma GCC optimize("omit-frame-pointer")
#pragma GCC optimize("unroll-loops")

using namespace std;
using u = long long unsigned int;
using l = long long int;
using d = long double;
enum color { red, green, blue };

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  u n;
  l dp[3] = {};
  cin >> n;
  while (n--) {
    u t;
    l r, g, b;
    cin >> t;
    r = max(dp[color::green] - t, dp[color::blue] - t);
    g = max(dp[color::red] + t, dp[color::blue] + t);
    b = max(dp[color::red], dp[color::green]);
    dp[color::red] = r;
    dp[color::green] = g;
    dp[color::blue] = b;
  }
  cout << *max_element(dp, dp + 3) << '\n';
  return 0;
}