#include <bits/stdc++.h>
using namespace std;
int n;
long long a[100010], f[100010][70];
int main(){
    ios::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
    cin >> n;
    for (int i = 1; i <= n; ++i)cin >> a[i];
    fill_n(f[1], 70, 1);
    for (int i = 2; i <= n; ++i){
        long long ds = a[i] - a[i - 1];int dp = __lg(ds);
        if (dp == 0)f[i][0] = f[i - 1][0] + 1;
        else {
            for (int j = 0; j < dp; ++j)f[i][j] = f[i - 1][j] + (1ll << j);
            long long Rst = ds - (1ll << dp), lst = 1ll << dp - 1;
            //cnt of nodes in last storey(must not full,maybe 0),cnt of nodes in last full storey
            f[i][dp] = max(f[i - 1][dp] + Rst, f[i - 1][dp - 1] + max(Rst, lst) + !!Rst);
        }
        for (int j = dp + 1; j <= 62; ++j)f[i][j] = max(f[i][j], f[i - 1][j]);
        for (int j = 1; j <= 62; ++j)f[i][j] = max(f[i][j], f[i][j - 1]);
    }
    cout << f[n][62] << endl;
    return 0;
}
/*
3
1 5 20

11


7
2 3 6 14 15 21 28
13
*/