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#include <iostream>

using namespace std;


int main() {
    ios_base::sync_with_stdio(false);

    int z;
    cin >> z;

    long long num;
    long long sum = 0;

    while (z--) {
        cin >> num;
        sum = sum + (1 << num);
    }

    long long result = 1;
    int counter = 0;

    while (result <= sum) {
        result =  (result << 1);
        counter++;
    }

    if (result > sum) {
        counter--;
    }
    cout << counter << endl;
}