import math
import sys

def val(v1, v2):
    return v1 + v2 - math.floor(math.log((v2 - v1), 2))


count = int(sys.stdin.readline())
values = sys.stdin.readline().strip().split(' ')
values = map(long, values)
max = -1000000

for i in range(count - 1):
    for j in range(i + 1, count):
        if values[j] > values[i]:
            res = val(values[i], values[j])
            if res > max:
                max = res

print int(max)