#include <bits/stdc++.h>
using namespace std;
long long n, a[1000005], mini[1000005], maxi[1000005], res;
int main() {
    ios_base::sync_with_stdio(0);
    cin.tie();
    cout.tie();
    // freopen(".INP", "r", stdin);
    // freopen(".OUT", "w", stdout);
    cin >> n;
    for (long long i = 1; i <= n; i++) {
        cin >> a[i];
    }
    maxi[1] = a[1] * 2;
    for (long long i = 2; i <= n; i++) {
        maxi[i] = max(maxi[i - 1], a[i] * 2);
    }
    mini[n] = a[n];
    for (long long i = n - 1; i >= 1; i--) {
        mini[i] = min(mini[i + 1], a[i]);
    }
    res = 0;
    for (long long i = 2; i <= n - 1; i++) {
        res = max(res, maxi[i - 1] - a[i] - mini[i + 1]);
    }
    cout << res;
}