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 C
    {
        class Program
        {
            static int[] ToIntAry(string[]str)
            {
                int len = str.Length;
                int[] intary = new int[len];
                for(int i = 0; i < len;i++)
                {
                    intary[i] = int.Parse(str[i]);
                }
                return intary;
            }
            static void Main(string[] args)
            {
                int[] NM = ToIntAry(Console.ReadLine().Split(' '));
                int n = NM[0], m = NM[1];
                int[] input = ToIntAry(Console.ReadLine().Split(' '));
                int[] Hs = new int[n+1];
                input.CopyTo(Hs,1);
                bool[] Score = new bool[n+1];
                Score[0] = true;
                for(int i = 1; i <= n;i++)
                {
                    Score[i] = default;
                }
                int Count = 0;
                int a,b;
                for(int i = 0;i < m;i++)
                {
                    input = ToIntAry(Console.ReadLine().Split(' '));
                    a = input[0];
                    b = input[1];
                    if(Hs[a] < Hs[b])
                    {
                        Score[a] = true;
                    }else{
                        Score[b] = true;
                    }
                }
     
                foreach(bool s in Score)
                {
                    if (!s)
                    {
                        Count++;
                    }
                }
                Console.WriteLine(Count);
            }
        }
    }