chef.cpp

#include <iostream>

#define for0(i, n) for (int i = 0; i < (int)(n); ++i)            // 0 based indexing
#define for1(i, n) for (int i = 1; i <= (int)(n); ++i)           // 1 based indexing
#define forc(i, l, r) for (int i = (int)(l); i <= (int)(r); ++i) // closed interver from l to r r inclusive
#define forr0(i, n) for (int i = (int)(n)-1; i >= 0; --i)        // reverse 0 based.
#define forr1(i, n) for (int i = (int)(n); i >= 1; --i)          // reverse 1 based

// short hand for usual tokens
#define pb push_back
#define fi first
#define se second
#define inf 1e18
#define bitc(n) __builtin_popcount(n)
// to be used with algorithms that processes a container Eg: find(all(c),42)
#define all(x) (x).begin(), (x).end()  // Forward traversal
#define rall(x) (x).rbegin, (x).rend() // reverse traversal

// traversal function to avoid long template definition. Now with C++11 auto alleviates the pain.
#define tr(c, i) for (__typeof__((c)).begin() i = (c).begin(); i != (c).end(); i++)

// find if a given value is present in a container. Container version. Runs in log(n) for set and map
#define present(c, x) ((c).find(x) != (c).end())

// find version works for all containers. This is present in std namespace.
#define cpresent(c, x) (find(all(c), x) != (c).end())

// Avoiding wrap around of size()-1 where size is a unsigned int.
#define sz(a) int((a).size())

using namespace std;

// Shorthand for commonly used types
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int, int> ii;
typedef vector<ii> vii;
typedef long long ll;
typedef vector<ll> vll;
typedef vector<vll> vvll;
typedef double ld;

void solve()
{

    ll n;
    cin >> n;
    vector<ll> arr(n);
    ll ct = 0;
    ll ans = 0;
    for (ll i = 0; i < n; i++)
    {
        cin >> arr[i];
        if (arr[i] < 0)
        {
            ct++;
            arr[i] = -arr[i];
        }
        ans += arr[i];
    }
    sort(all(arr));
    if (ct & 1)
        ans -= 2 * arr[0];
    cout << ans;
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.precision(10);
    cout << fixed;

    // ll t;
    // cin>>t;
    // while(t--)
    solve();
    return 0;
}