#include <bits/stdc++.h>
using namespace std;
#define int long long
int n;
int a[100010];
int M(int l, int r)
{
    if (abs(r - l) <= 5) {
        int ans = 0;
        for (int i = l; i <= r; i++) {
            if (a[i] > ans) ans = a[i];
        }
        return ans;
    }
    else {
        return (M(l, (l + r) / 2) % max(M(((l + r) / 2) + 1, r), (long long) 7) + (a[(l + r) / 2]) - 1);
    }
}
signed main()
{
    cin >> n;
    for (int i = 1; i <= n; i++)
        cin >> a[i];
    cout << M(1, n);
    return 0;
}