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

    ll ans = 0;
    rep(i, n) ans += abs(a[i]);

    cout << ans << "\n";
}