import sys
import heapq

def can_finish(H, t, powers):
    """Return True if we can finish all monsters with t attacks.
       We assume `powers` is a list of 2^k values for k=0..(max_needed-1).
    """
    if t == 0:
        return all(h <= 0 for h in H)
    # heap of negatives for max-heap
    heap = [-h for h in H if h > 0]
    if not heap:
        return True
    heapq.heapify(heap)
    # use largest powers first: powers[t-1], ..., powers[0]
    for k in range(t - 1, -1, -1):
        if not heap:
            return True
        largest = -heapq.heappop(heap)
        largest -= powers[k]
        if largest > 0:
            heapq.heappush(heap, -largest)
    return not heap

def main():
    data = list(map(int, sys.stdin.buffer.read().split()))
    if not data:
        return
    it = iter(data)
    n = int(next(it))
    H = [int(next(it)) for _ in range(n)]

    # safe upper bound: N + 60 (2^60 >= 1e18)
    MAX_EXTRA = 60
    hi_bound = n + MAX_EXTRA

    # Precompute powers 2^0 ... 2^(hi_bound-1)
    powers = [1 << i for i in range(hi_bound)]

    lo, hi = 0, hi_bound
    while lo < hi:
        mid = (lo + hi) // 2
        if can_finish(H, mid, powers):
            hi = mid
        else:
            lo = mid + 1
    print(lo)

if __name__ == "__main__":
    main()