#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  cin.tie(nullptr)->sync_with_stdio(false);
  int n;
  cin >> n;
  vector<ll> a(n);
  rep(i, n) cin >> a[i];
  sort(a.rbegin(), a.rend());
  rep(i, n - 1) if (abs(a[i]) > abs(a[i + 1])) a[i + 1] = a[i];
  cout << accumulate(a.begin(), a.end(), 0LL, [](ll x, ll y) {
    return x + abs(y);
  }) << '\n';
  return 0;
}