#include <bits/stdc++.h>
using namespace std;

#define For(i, a, b) for(int i = (a); i < (b); i++)
#define rep(i, n) For(i, 0, n)
#define rFor(i, a, b) for(int i = (a); i >= (b); i--)
#define ALL(v) (v).begin(), (v).end()
#define rALL(v) (v).rbegin(), (v).rend()

using lint = long long;
using ld = long double;

int INF = 2000000000;
lint LINF = 1000000000000000000;

struct SetupIo {
    SetupIo() {
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
        cout << fixed << setprecision(15);
    }
} setupio;

int main() {
    int n;
    cin >> n;
    vector<lint> c(n);
    rep(i, n) {
        cin >> c[i];
    }
    lint a = c[0], b = c.back();
    if (a <= 0 && 0 <= b) {
        cout << (b - a) * 2LL << "\n";
    } else if (a >= 0) {
        cout << b * 2LL << "\n";
    } else {
        cout << -a * 2LL << "\n";
    }
}