#include <bits/stdc++.h>
#define cs const
#define pb push_back
using namespace std;

typedef __int128_t i128; 
cs int N = 1e3 + 5, M = 105; 

int n, f[N][M], g[N][M];
i128 a[N];

i128 read() {
    i128 x = 0; char c = getchar(); 
    while(!isdigit(c)) c = getchar(); 
    while(isdigit(c)) x = x * 10 + c - '0', c = getchar(); 
    return x; 
}
int lg(i128 x) {
    int res = 0; 
    while(x) x >>= 1, res++; 
    return res - 1; 
}
void out(i128 x){
    if(x > 9) out(x / 10); 
    putchar(x % 10 + '0'); 
}

int main() {
    #ifdef zqj
    freopen("1.in","r",stdin);
    #endif
    cin >> n; 
    for(int i = 1; i <= n; i++) a[i] = read();
    memset(f, 0x3f, sizeof f);
    memset(g, 0x3f, sizeof g);
    for(int i = 1; i <= n; i++) {
        f[i][lg(a[i])] = i; 
    }
    int ans = 0; 
    for(int i = 0; i <= 120; i++) {
        for(int j = n; j; j--) {
            int p = f[j][i];
            g[j][i] = min(f[j][i], g[j + 1][i]);
            if(p <= n) ans = i; 
            ++ p; 
            if(p > n) continue; 
            // cout << i << ' ' << j << ' ' << f[j][i] <<' ' << g[p][i] << endl;
            f[j][i + 1] = g[p][i]; 
        }
    }
    out((i128)1 << ans);
    return 0; 
}