#include <bits/stdc++.h>
using namespace std;

int main() {
  int N, Min = 1e9; cin >> N;
  bool B = true;
  vector DP(N + 1, vector<long long>(2, -1e18));
  DP.at(0).at(0) = 0;
  for (int i = 0; i < N; i++) {
    int A; cin >> A;
    if (A <= 0) B = false;
    else Min = min(Min, A);
    DP.at(i + 1).at(1) = max(DP.at(i).at(1), DP.at(i).at(0) + A * -1);
    DP.at(i + 1).at(0) = max(DP.at(i).at(0), DP.at(i).at(1) + A);
  }
  cout << (B ? (long long)-Min : max(DP.at(N).at(0), DP.at(N).at(1))) << endl;
}