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

using ll = long long;
#define rep(i, n) for(int i = 0; i < n; i++)

int main() {
	int N;
	cin >> N;
	vector<int> c(N);
	rep(i, N) cin >> c[i];
	int ans = 1e9;
	if(c[0] >= 0) ans = c[N - 1] * 2;
	else if(c[N - 1] <= 0) ans = abs(c[0]) * 2;
	else ans = (abs(c[0]) + c[N - 1]) * 2;
	cout << ans << endl;
}