import heapq
n=int(input())
h=list(map(int,input().split()))
#print(h)
lef=n-1
rig=n+80
S=sum(h)
while(rig-lef>1) :
    mid=(rig+lef)//2
    hq=[]
    if(mid<=60 and 2**mid-1<S) :
        lef=mid
        continue
    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=min(1<<i,10**18+1)
        p=heapq.heappop(hq)*-1
        if(p-dec>0) :
            heapq.heappush(hq,-(p-dec))
    if(len(hq)==0) :
        rig=mid
    else :
        lef=mid

print(rig)