import sys
input = sys.stdin.readline
from collections import *

N = int(input())
A = list(map(int, input().split()))
cnt = Counter(A)
s = 0

for i in range(10**6):
    s += cnt[i]
    
    if cnt[i]>=2:
        continue
    else:
        if cnt[i]==0 or s==N:
            print(i)
        else:
            print(i+1)
            
        break