#include <iostream>
using namespace std;
int main()
{
    int n;
    cin >> n;
    int *Candy = new int[n];
    for (int i = 0; i < n; i++)
    {
        cin >> Candy[i];
    }
    int total = 0;
    while (1)
    {
        bool flag = true;
        for (int i = 1; i < n; i++)
        {
            if (Candy[0] != Candy[i])
            {
                flag = false;
                break;
            }
        }
        if (flag == true)
            break;
        int temp = Candy[n - 1];
        for (int i = n - 1; i >= 0; i--)
        {
            if (i == 0)
            {
                Candy[0] = Candy[0] / 2 + temp / 2;
            }
            else
                Candy[i] = Candy[i] / 2 + Candy[i - 1] / 2;
            if (Candy[i] % 2 == 0)
            {
                Candy[i] += 1;
                total += 1;
            }
        }
    }
    cout << total << endl;
}