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;

namespace oasobi
{
    static class MainClass
    {
        public static void Main()
        {
            string[] input = Console.ReadLine().Split(' ');
            int n = int.Parse(input[0]);
            int m = int.Parse(input[1]);

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

            int[] H = new int[n];

            for(int i = 0; i < n; ++i)
            {

                H[i] = int.Parse(h[i]);
            }

            int[,] AB = new int[m, 2];

            for(int i = 0; i < m; ++i)
            {
                string[] ab = Console.ReadLine().Split(' ');
                AB[i, 0] = int.Parse(ab[0]);
                AB[i, 1] = int.Parse(ab[1]);
            }

            int counter = 0;//ここまでセッティング

            for(int i = 0; i < n; ++i)//N個の展望台について一個ずつ調べるよ
            {
                bool good = true;

                for(int j = 0; j < m; ++j)//ABの組から第i展望台に繋がってるものを炙り出すよ
                {
                    if(AB[j,0] == i)//A側がi
                    {
                        if(H[i] <= H[AB[j,1]-1])
                        {
                            good = false;
                            break;
                        }
                    }
                    else if(AB[j,1] == i)//B側がi
                    {
                        if(H[i] <= H[AB[j,0]-1])
                        {
                            good = false;
                            break;
                        }

                    }
                }

                if(good == true)
                {
                    ++counter;
                }
            }

            Console.WriteLine(counter);
        }
    }
}