def binary_search(f):
    left,right=0,10**5 + 80
    while right-left>1:
        mid=(right+left)//2
        if f(mid):
            right=mid
        else:
            left=mid
    return right

def f(x):
    hq = [-h for h in H]
    heapq.heapify(hq)
    for i in range(x-1,-1,-1):
        if len(hq) == 0:
            break
        if i>=60:
            t = 2**60
        else:
            t = 2**i
        p = heapq.heappop(hq)
        p += t
        if p<0:
            heapq.heappush(hq, p)
    if len(hq) == 0:
        return True
    return False

import heapq
N=int(input())
H=list(map(int,input().split()))
print(binary_search(f))