Problem:
Score : 300 points

Problem Statement

There are N observatories in AtCoder Hill, called Obs. 1, Obs. 2, ..., Obs. N. The elevation of Obs. i is H_i.
There are also M roads, each connecting two different observatories. Road j connects Obs. A_j and Obs. B_j.

Obs. i is said to be good when its elevation is higher than those of all observatories that can be reached from Obs. i using just one road.
Note that Obs. i is also good when no observatory can be reached from Obs. i using just one road.

How many good observatories are there?

Constraints

2 \leq N \leq 10^5

1 \leq M \leq 10^5

1 \leq H_i \leq 10^9

1 \leq A_i,B_i \leq N

A_i \neq B_i

Multiple roads may connect the same pair of observatories.

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N M
H_1 H_2 ... H_N
A_1 B_1
A_2 B_2
:
A_M B_M

Output

Print the number of good observatories.

Sample Input 1

4 3
1 2 3 4
1 3
2 3
2 4

Sample Output 1

2

From Obs. 1, you can reach Obs. 3 using just one road. The elevation of Obs. 1 is not higher than that of Obs. 3, so Obs. 1 is not good.

From Obs. 2, you can reach Obs. 3 and 4 using just one road. The elevation of Obs. 2 is not higher than that of Obs. 3, so Obs. 2 is not good.

From Obs. 3, you can reach Obs. 1 and 2 using just one road. The elevation of Obs. 3 is higher than those of Obs. 1 and 2, so Obs. 3 is good.

From Obs. 4, you can reach Obs. 2 using just one road. The elevation of Obs. 4 is higher than that of Obs. 2, so Obs. 4 is good.

Thus, the good observatories are Obs. 3 and 4, so there are two good observatories.

Sample Input 2

6 5
8 6 9 1 2 1
1 3
4 2
4 3
4 6
4 6

Sample Output 2

3

Solution in C# (.NET Core 3.1.201) (judge verdict: Wrong Answer)

using System;
using System.Collections.Generic;

namespace test
{
    class MainClass
    {
        public static void Main(string[] args)
        {

            //問題166

            string[] line = Console.ReadLine().Split(' ');
            int N = int.Parse(line[0]);
            int M = int.Parse(line[1]);

            string[] line2 = Console.ReadLine().Split(' ');

            int[] H = new int[N];
            for (int i = 0; i < N; i++)
            {
                H[i] = int.Parse(line2[i]);
            }

            int[] A = new int[M];
            int[] B = new int[M];

            for (int i = 0; i < M; i++)
            {
                string[] line3 = Console.ReadLine().Split(' ');
                A[i] = int.Parse(line3[0]);
                B[i] = int.Parse(line3[1]);
            }

            List<int> ans = new List<int>();

            for (int i = 0; i<N; i++)
            {
                ans.Add(i);
            }

            
            for (int i = 0; i < M; i++) 
            {
                //Console.WriteLine(i);

                if (H[A[i] - 1] < H[B[i] - 1])
                {
                    int num = ans.IndexOf(A[i] - 1);

                    //Console.WriteLine(i);

                    //Console.WriteLine("aaa");

                    //Console.WriteLine(num);


                    if (num >= 0)
                    {
                        //Console.WriteLine(i);
                        //Console.WriteLine(num);

                        ans.RemoveAt(num);

                    }
                }
                else
                {
                    int num = ans.IndexOf(B[i] - 1);

                    if (num >= 0)
                    {
                        ans.RemoveAt(num);
                    }

                }

                //foreach (int a in ans)
                //{
                //    Console.WriteLine(a);
                //}
            }

            Console.WriteLine(ans.Count);

            foreach (int a in ans)
            {
                //Console.WriteLine(a);
            }

        }


    }
}