#include <bits/stdc++.h>
using namespace std;

const int N = 1e3 + 5;

#define ll __int128

int n;
ll A[N];

char s[N];

vector < ll > all;

void read(ll &x) {
    char c = getchar();
    x = 0;
    while(!isdigit(c)) {
        c = getchar();
    }
    while(isdigit(c)) {
        x = x * 10 + c - '0';
        c = getchar();
    }
}

void write(int x) {
    if(!x) return;
    write(x / 10);
    cout << (int)(x % 10);
}

int main() {
    scanf("%d", &n);
    for(int i = 1; i <= n; ++ i) {
        read(A[i]);
        if(!all.size()) {
            all.push_back(A[i]);
            continue;
        }
        while(all.size() && all.back() < A[i]) all.pop_back();
        all.push_back(A[i]);
        while(all.size() >= 2 && all.back() == all[all.size() - 2]) {
            all.pop_back();
            all[all.size() - 1] *= 2;
        }
    }
    write(all[0]);
}