import heapq
n=int(input())
h=list(map(int,input().split()))
#print(h)
lef=-1
rig=80
while(rig-lef>1) :
    mid=(rig+lef)//2
    hq=[]
    heapq.heapify(hq)
    for i in range(n) :
        heapq.heappush(hq,-h[i])
    for i in range(mid-1,-1,-1):
        if(len(hq)==0) :
            break
        dec=1<<i
        p=-hq[0]
        heapq.heappop(hq)
        if(p-dec>0) :
            heapq.heappush(hq,-(p-dec))
    if(len(hq)==0) :
        rig=mid
    else :
        lef=mid

print(rig)