#include <iostream>
#include <vector>
using namespace std;

int main() {
    int N;
    cin >> N;
    vector<int> c(N);
    for (int i = 0; i < N; i++) {
        cin >> c[i];
    }
    int ans = 0;
    if (c[N - 1] > 0) {
        ans += 2 * c[N - 1];
    }
    if (c[0] < 0) {
        ans += 2 * (-c[0]);
    }
    cout << ans << endl;
}