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

#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;

template <class T> using v = vector<T>;
using ll = long long;
using dd = long double;
using int2 = pair<int, int>;
using ll2 = pair<ll, ll>;
using dd2 = pair<dd, dd>;

#define f first
#define s second
#define all(x) begin(x), end(x)
istream &__cin = cin;
#ifdef DEV_MODE
#include "debug.h"
__cinwrapper __cin_wrapper;
#define cin __cin_wrapper
#else
#define dbg(...)
#define dbg2d(...)
#endif

template <class T1, class T2>
istream &operator>>(istream &in, pair<T1, T2> &p) {
  in >> p.first >> p.second;
  return in;
}
template <class T> istream &operator>>(istream &in, v<T> &v) {
  for (auto &x : v)
    in >> x;
  return in;
}
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());

/*
 _______________________________________
( If you don't fail at least 90% of the )
( time, you're not aiming high enough.  )
(                                       )
( - Alan Kay                            )
 ---------------------------------------
        o   ^__^
         o  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||
*/

const bool INTERACTIVE = false;
const bool MULTITEST = false;
/******************************************************************************/

#pragma region templates
using i128 = __int128;
ostream &operator<<(ostream &out, i128 x) {
  if (x == 0)
    return out << "0";
  string y = "";
  bool neg = x < 0;
  if (neg)
    x = -x;
  while (x) {
    y.push_back((char)(x % 10) + '0');
    x /= 10;
  }
  if (neg) {
    y.push_back('-');
  }
  reverse(all(y));
  return out << y;
}
#pragma endregion templates

const string vals[] = {"1",
                       "2",
                       "4",
                       "8",
                       "16",
                       "32",
                       "64",
                       "128",
                       "256",
                       "512",
                       "1024",
                       "2048",
                       "4096",
                       "8192",
                       "16384",
                       "32768",
                       "65536",
                       "131072",
                       "262144",
                       "524288",
                       "1048576",
                       "2097152",
                       "4194304",
                       "8388608",
                       "16777216",
                       "33554432",
                       "67108864",
                       "134217728",
                       "268435456",
                       "536870912",
                       "1073741824",
                       "2147483648",
                       "4294967296",
                       "8589934592",
                       "17179869184",
                       "34359738368",
                       "68719476736",
                       "137438953472",
                       "274877906944",
                       "549755813888",
                       "1099511627776",
                       "2199023255552",
                       "4398046511104",
                       "8796093022208",
                       "17592186044416",
                       "35184372088832",
                       "70368744177664",
                       "140737488355328",
                       "281474976710656",
                       "562949953421312",
                       "1125899906842624",
                       "2251799813685248",
                       "4503599627370496",
                       "9007199254740992",
                       "18014398509481984",
                       "36028797018963968",
                       "72057594037927936",
                       "144115188075855872",
                       "288230376151711744",
                       "576460752303423488",
                       "1152921504606846976",
                       "2305843009213693952",
                       "4611686018427387904",
                       "9223372036854775808",
                       "18446744073709551616",
                       "36893488147419103232",
                       "73786976294838206464",
                       "147573952589676412928",
                       "295147905179352825856",
                       "590295810358705651712",
                       "1180591620717411303424",
                       "2361183241434822606848",
                       "4722366482869645213696",
                       "9444732965739290427392",
                       "18889465931478580854784",
                       "37778931862957161709568",
                       "75557863725914323419136",
                       "151115727451828646838272",
                       "302231454903657293676544",
                       "604462909807314587353088",
                       "1208925819614629174706176",
                       "2417851639229258349412352",
                       "4835703278458516698824704",
                       "9671406556917033397649408",
                       "19342813113834066795298816",
                       "38685626227668133590597632",
                       "77371252455336267181195264",
                       "154742504910672534362390528",
                       "309485009821345068724781056",
                       "618970019642690137449562112",
                       "1237940039285380274899124224",
                       "2475880078570760549798248448",
                       "4951760157141521099596496896",
                       "9903520314283042199192993792",
                       "19807040628566084398385987584",
                       "39614081257132168796771975168",
                       "79228162514264337593543950336",
                       "158456325028528675187087900672",
                       "316912650057057350374175801344",
                       "633825300114114700748351602688",
                       "1267650600228229401496703205376"};

void solve() {
  int n;
  cin >> n;
  v<int> a(n);
  for (int i = 0; i < n; i++) {
    string s;
    cin >> s;
    while (vals[a[i]] != s)
      a[i]++;
  }

  v<v<int>> dp(n, v<int>(101, 1e9));
  for (int i = 0; i < n; i++) {
    dp[i][a[i]] = i;
  }
  i128 ans = 1;
  for (int j = 0; j < 100; j++) {
    for (int i = n - 1; i >= 0; i--) {
      if (i < n - 1)
        dp[i][j] = min(dp[i][j], dp[i + 1][j]);
      if (dp[i][j] < n - 1)
        dp[i][j + 1] = min(dp[i][j + 1], dp[dp[i][j] + 1][j]);
    }
    if (dp[0][j + 1] < n)
      ans = (i128)1 << (j + 1);
  }
  cout << ans;
}

int main() {
#ifdef DEV_MODE
  debug_start(INTERACTIVE, "d.txt");
#else
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
#endif
  int t;
  if (MULTITEST)
    cin >> t;
  else
    t = 1;
  while (t--)
    solve();

#ifdef DEV_MODE
  debug_exit(INTERACTIVE);
#endif
}
#ifdef DEV_MODE
#include "debug.cpp"
#endif