#!/bin/python3

import sys

def longestSequence(a):
    for i in a:
        val = check_power_of_2(i)

        if val[0] == i:
            return (i << 1) - 1
        

def check_power_of_2(a):
    i = 1
    counter = 0
    while(i < a):
        i = i << 1
        counter += 1
    
    return i,counter
    
if __name__ == "__main__":
    n = int(input().strip())
    a = list(map(int, input().strip().split(' ')))
    result = longestSequence(a)
    print(result)