class BIT:
    def __init__(self, n):
        self.size = n
        self.tree = [0]*(n+1)
 
    def build(self, list):
        self.tree[1:] = list.copy()
        for i in range(self.size+1):
            j = i + (i & (-i))
            if j < self.size+1:
                self.tree[j] += self.tree[i]

    def sum(self, i):
        # [0, i) の要素の総和を返す
        s = 0
        while i>0:
            s += self.tree[i]
            i -= i & -i
        return s
    # 0 index を 1 index に変更  転倒数を求めるなら1を足していく
    def add(self, i, x):
        i += 1
        while i <= self.size:
            self.tree[i] += x
            i += i & -i

    # 総和がx以上になる位置のindex をbinary search
    def bsearch(self,x):
        le = 0
        ri = 1<<(self.size.bit_length()-1)
        while ri > 0:
            if le+ri <= self.size and self.tree[le+ri]<x:
                x -= self.tree[le+ri]
                le += ri
            ri >>= 1
        return le+1

from heapq import heappop, heappush

n = int(input())
A = list(map(int,input().split()))
M = 10**5
use = [0]*(M+1)
use[0] = 1
ans = 0
h = [[-M,0]]
bit = BIT(M+2)
bit.add(0,1)
bit.add(M+1,1)

for a in A:
    if use[a]:
        continue
    ans += 1
    num = bit.sum(a)

    ind = bit.bsearch(num)-1
    now = a-ind
    l = []
    while h and -h[0][0] >= now:
        size,lind = heappop(h)
        size *= -1
        use[lind+now] = 1
        bit.add(lind+now,1)
        l.append([-now+1,lind])
        l.append([-size+now,lind+now])
    for nex in l:
        heappush(h,nex)
print(ans)