#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;
}
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