#include <bits/stdc++.h>
using namespace std;
int main() {
    int n;
    cin >> n;
    vector<int> c(n);
    for (int i = 0; i < n; i++) cin >> c[i];

    int l = c[0], r = c[n - 1];
    int ans;
    if (0 <= l) ans = r * 2;
    else if (r <= 0) ans = abs(l) * 2;
    else ans = abs(l - r) * 2;
    cout << ans << endl;
    return 0;
}