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#include <iostream>
#include <vector>
#include <cmath>

using namespace std;

int main() {
    int n;
    cin >> n;

    vector<int> coins;

    for (int i = 0; i < n; ++i) {
        int a;
        cin >> a;
        coins.push_back(a);
    }

    double coinsValueSum = 0;

    for (int j = 0; j < n; ++j) {
        double add = pow(2, coins[j]);
        coinsValueSum += add;
    }

    int a = 1;
    double maxPower = 0;
    while (true) {
        double power = pow(2, a);
        if (power < coinsValueSum) {
            maxPower = power;
        } else {
            break;
        }
        a++;
    }

/*    cout << coinsValueSum << endl;
    cout << maxPower << endl;*/

    double result = log2(maxPower);
    cout << result << endl;
}