s=[0 for i in range(105+10)]
n=int(input())
f=list(map(int,input().split()))
for i in f:
if i<105:
s[i]+=1
for i in range(1,10**5+1):
if s[i]%(i+1)!=0:
print(i)
exit()
s[i+1]=s[i+1]+s[i]//(i+1)
print(min(f))