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#include <iostream>
#include <algorithm>

using namespace std;

int n;
const int MAXN = 1e6;
const int MAXA = 201718;

int ta[MAXA+1];

int last = 0;

void read() {
    cin >> n;
    
    for(int i = 0; i < n; ++i) {
        int a;
        cin >> a;
        ta[a]++;
        last = max(last, a);
    }
}

bool DFS_can(int index, int amount) {
    if(index < 0 || amount > 1000000) return false;
    
    amount -= ta[index];
    if(amount <= 0) return true;
    
    return DFS_can(index-1, amount*2);
}

int max_ans() {
    for(int i = 19; i >= 0; --i) {
        if(DFS_can(last, 1 << i)) return i;
    }
    return 0;
}

int main() {
    ios_base::sync_with_stdio(false);
    read();
    
    cout << (max_ans() + last) << endl;
    
    return 0;
}