Problem:
Score : 300 points

Problem Statement

You are given a sequence of positive integers of length N, a = (a_1, a_2, ..., a_N).
Your objective is to remove some of the elements in a so that a will be a good sequence.

Here, an sequence b is a good sequence when the following condition holds true:

For each element x in b, the value x occurs exactly x times in b.

For example, (3, 3, 3), (4, 2, 4, 1, 4, 2, 4) and () (an empty sequence) are good sequences, while (3, 3, 3, 3) and (2, 4, 1, 4, 2) are not.

Find the minimum number of elements that needs to be removed so that a will be a good sequence.

Constraints

1 \leq N \leq 10^5

a_i is an integer.

1 \leq a_i \leq 10^9

Input

Input is given from Standard Input in the following format:

N
a_1 a_2 ... a_N

Output

Print the minimum number of elements that needs to be removed so that a will be a good sequence.

Sample Input 1

4
3 3 3 3

Sample Output 1

1

We can, for example, remove one occurrence of 3. Then, (3, 3, 3) is a good sequence.

Sample Input 2

5
2 4 1 4 2

Sample Output 2

2

We can, for example, remove two occurrences of 4. Then, (2, 1, 2) is a good sequence.

Sample Input 3

6
1 2 2 3 3 3

Sample Output 3

0

Sample Input 4

1
1000000000

Sample Output 4

1

Remove one occurrence of 10^9. Then, () is a good sequence.

Sample Input 5

8
2 7 1 8 2 8 1 8

Sample Output 5

5

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Text;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
using static System.Math;

namespace AtCoder
{
    public class Program
    {



        public static void Main(string[] args)
        {
            Dictionary<int, int> pairs = new Dictionary<int, int>();
            ReadInt();
            var a = ReadInts();
            foreach(var i in a)
            {
                if (!pairs.ContainsKey(i))
                {
                    pairs.Add(i, 1);

                }
                else {
                    pairs[i] += 1;
                }
            }

            var sum = 0;
            foreach(var i in pairs)
            {
                if (i.Value < i.Key)
                {
                    sum += i.Value;
                }
                else {
                    sum += -i.Key + i.Value;

                }

            }

            Write(sum);




         }

        private static void Read2Ints(out int a, out int b)
        {
            var temp = ReadInts();
            a = temp[0];
            b = temp[1];
        }
        private static void Read3Ints(out int a, out int b, out int c)
        {
            var temp = ReadInts();
            a = temp[0];
            b = temp[1];
            c = temp[2];
        }

        private static void Write(IEnumerable<string> target, string sep = " ") { Console.WriteLine(string.Join(sep, target)); }
        private static void Write(IEnumerable<double> target, string sep = " ") { Console.WriteLine(string.Join(sep, target)); }
        private static void Write(IEnumerable<long> target, string sep = " ") { Console.WriteLine(string.Join(sep, target)); }
        private static void Writeints(IEnumerable<int> target, string sep = " ") { Console.WriteLine(string.Join(sep, target)); }
        private static void Write<T>(T str) { Console.WriteLine(str); }
        private static string[] ReadStrings() { return Console.ReadLine().Split(' '); }
        private static int ReadInt() { return int.Parse(Console.ReadLine()); }
        private static double ReadDouble() { return double.Parse(Console.ReadLine()); }
        private static int[] ReadInts() { return Console.ReadLine().Split(' ').Select(x => int.Parse(x)).ToArray(); }
        private static double[] ReadDoubles() { return Console.ReadLine().Split(' ').Select(x => double.Parse(x)).ToArray(); }

    }

}