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: Accepted)

using System;
using System.IO;
using System.Linq;
using System.Collections.Generic;
using System.Text;
using System.Numerics;

namespace abc166
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.SetOut(new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false });
            if (File.Exists("input.txt"))
            {
                Console.SetIn(new StreamReader("input.txt"));
            }
			solve_abc166C();
			Console.Out.Flush();

        }
        public static void solve_abc166C()
        {
            int[] nm = Array.ConvertAll(Console.ReadLine().Split(), int.Parse);
            int n = nm[0];
            int m = nm[1];
            int[] h = Array.ConvertAll(Console.ReadLine().Split(), int.Parse);
            Dictionary<int, int> g = new Dictionary<int, int>();
            for (int i = 1; i <= n; i++)
            {
                g.Add(i, 0);
            }
            int cnt = 0;
            while (m-- > 0)
            {
                int[] ab = Array.ConvertAll(Console.ReadLine().Split(), int.Parse);
                if (h[ab[0] - 1] > h[ab[1] - 1])
                {
                    if (g[ab[0]] >= 0)
                    {
                        g[ab[0]]++;
                    }
                    g[ab[1]] = -1;
                }
                else if (h[ab[1] - 1] > h[ab[0] - 1])
                {
                    if (g[ab[1]] >= 0)
                    {
                        g[ab[1]]++;
                    }
                    g[ab[0]] = -1;
                }
                else
                {
                    g[ab[0]] = -1;
                    g[ab[1]] = -1;
                }
            }
            foreach (var item in g)
            {
                if (item.Value >= 0)
                {
                    cnt++;
                }
            }
            Console.WriteLine(cnt);
        }

        public static void solve_abc166B()
        {
            int[] nk = Array.ConvertAll(Console.ReadLine().Split(), int.Parse);
            int n = nk[0];
            int k = nk[1];
            int[] cnt = new int[n];
            while (k-- > 0)
            {
                int d = Convert.ToInt32(Console.ReadLine());
                int[] a = Array.ConvertAll(Console.ReadLine().Split(), int.Parse);
                for (int i = 0; i < d; i++)
                {
                    cnt[a[i] - 1]++; 
                }
            }
            int sum = 0;
            for (int i = 0; i < cnt.Length; i++)
            {
                if (cnt[i] == 0)
                {
                    sum++;
                }
            }
            Console.WriteLine(sum);
        }

        public static void solve_abc166A()
        {
            string s = Console.ReadLine();
            if (s == "ABC")
            {
                Console.WriteLine("ARC");
            }
            else
            {
                Console.WriteLine("ABC");
            }
        }
    }
}