N = int(input())
L = list(map(int,input().split()))
d = {}
for i in L:
try:
d[i] += 1
except:
d[i] = 1
L = sorted(list(d.items()), key = lambda t : t[0])
ans = 0
for i in L:
if N <= i[0]:
ans = max(ans , N)
N -= i[1]
print(ans)