import heapq
N = int(input())
H = list(map(lambda x:-int(x),input().split()))
SUM = sum(H)

ng,ok = N-1,N+61
while(ok - ng > 1):
    mid = (ok+ng)//2
    if(mid < 60 and 2**mid < SUM):
        ng = mid
        continue
    now = H[:]
    heapq.heapify(now)
    p = 1
    atk = [min(1<<i,10**18) for i in range(mid-1,-1,-1)]
    for i in atk:
        if(not now):break
        v = heapq.heappop(now);v *= -1
        if(v > i):heapq.heappush(now,-(v-i))

    if(len(now) == 0):
        ok = mid
    else:
        ng = mid
print(ok)