Buggy python submission (verdict: Time Limit Exceeded):
#!usr/bin/env python3
from collections import defaultdict
from heapq import heappush, heappop
import sys
import math
import bisect
def LI(): return list(map(int, sys.stdin.readline().split()))
def I(): return int(sys.stdin.readline())
def LS(): return sys.stdin.readline().split()
def S(): return list(sys.stdin.readline())
def IR(n): return [I() for i in range(n)]
def LIR(n): return [LI() for i in range(n)]
def SR(n): return [S() for i in range(n)]
def LSR(n): return [LS() for i in range(n)]
mod = 1000000007
 
#A
"""
a, b = LI()
print((a+b+1)//2)
"""
 
#B
"""
a = S()
a = a[:-1]
b = S()
b = b[:-1]
a.sort()
b.sort(reverse=True)
if a < b:
    print("Yes")
else:
    print("No")
"""
 
#C
n = I()
a = LI()
seta = set(a)
ans = 0
for i in seta:
    x = a.count(i)
    if x != 0 and x >= i:
        ans += x - i
    else:
        ans += x
print(ans)

Fixed submission:
#!usr/bin/env python3
from collections import defaultdict
from heapq import heappush, heappop
import sys
import math
import bisect
def LI(): return list(map(int, sys.stdin.readline().split()))
def I(): return int(sys.stdin.readline())
def LS(): return sys.stdin.readline().split()
def S(): return list(sys.stdin.readline())
def IR(n): return [I() for i in range(n)]
def LIR(n): return [LI() for i in range(n)]
def SR(n): return [S() for i in range(n)]
def LSR(n): return [LS() for i in range(n)]
mod = 1000000007

#A
"""
a, b = LI()
print((a+b+1)//2)
"""

#B
"""
a = S()
a = a[:-1]
b = S()
b = b[:-1]
a.sort()
b.sort(reverse=True)
if a < b:
    print("Yes")
else:
    print("No")
"""

#C
n = I()
a = LI()
a.sort()
seta = set(a)
ans = 0
for i in seta:
    x = bisect.bisect_right(a,i) - bisect.bisect_left(a,i)
    if x != 0 and x >= i:
        ans += x - i
    else:
        ans += x
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
#!usr/bin/env python3
from collections import defaultdict
from heapq import heappush, heappop
import sys
import math
import bisect
def LI(): return list(map(int, sys.stdin.readline().split()))
def I(): return int(sys.stdin.readline())
def LS(): return sys.stdin.readline().split()
def S(): return list(sys.stdin.readline())
def IR(n): return [I() for i in range(n)]
def LIR(n): return [LI() for i in range(n)]
def SR(n): return [S() for i in range(n)]
def LSR(n): return [LS() for i in range(n)]
mod = 1000000007

#A
"""
a, b = LI()
print((a+b+1)//2)
"""

#B
"""
a = S()
a = a[:-1]
b = S()
b = b[:-1]
a.sort()
b.sort(reverse=True)
if a < b:
    print("Yes")
else:
    print("No")
"""

#C
n = I()
a = LI()
seta = set(a)
ans = 0
for i in seta:
    x = a.count(i)
    if x != 0 and x >= i:
        ans += x - i
    else:
        ans += x
print(ans)        

Fixed submission:
#!usr/bin/env python3
from collections import defaultdict
from heapq import heappush, heappop
import sys
import math
import bisect
def LI(): return list(map(int, sys.stdin.readline().split()))
def I(): return int(sys.stdin.readline())
def LS(): return sys.stdin.readline().split()
def S(): return list(sys.stdin.readline())
def IR(n): return [I() for i in range(n)]
def LIR(n): return [LI() for i in range(n)]
def SR(n): return [S() for i in range(n)]
def LSR(n): return [LS() for i in range(n)]
mod = 1000000007

#A
"""
a, b = LI()
print((a+b+1)//2)
"""

#B
"""
a = S()
a = a[:-1]
b = S()
b = b[:-1]
a.sort()
b.sort(reverse=True)
if a < b:
    print("Yes")
else:
    print("No")
"""

#C
n = I()
a = LI()
a.sort()
seta = set(a)
ans = 0
for i in seta:
    x = bisect.bisect_right(a,i) - bisect.bisect_left(a,i)
    if x != 0 and x >= i:
        ans += x - i
    else:
        ans += x
print(ans)