#include using namespace std; void fast_io() { ios_base::sync_with_stdio(false); cin.tie(nullptr); } int main() { fast_io(); int n; cin >> n; vector c(n); for (int i = 0; i < n; i++) { cin >> c[i]; } int ans = max(0, c.back()) - min(0, c.front()); cout << ans * 2 << endl; }