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 Java (OpenJDK 11.0.6) (judge verdict: Accepted)

import java.io.BufferedInputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Scanner;

/**
 * Created by Harry on 5/3/20.
 */
public class Main {
    public static void main(String[] args) throws IOException {
        Scanner scanner = new Scanner(new BufferedInputStream(System.in));
        int n = scanner.nextInt();
        int m = scanner.nextInt();
        int[] h = new int[n+1];
        for(int i=0; i<n; i++){
            h[i+1] = scanner.nextInt();
        }
        int[][] edges = new int[m][2];
        for(int i=0; i<m; i++){
            edges[i][0] = scanner.nextInt();
            edges[i][1] = scanner.nextInt();
        }
        List<Integer>[] graph = new List[n+1];
        for(int i=1; i<=n; i++){
            graph[i] = new ArrayList<>();
        }
        for(int[] e : edges){
            graph[e[0]].add(e[1]);
            graph[e[1]].add(e[0]);
        }
        int res = 0;
        for(int o=1; o<=n; o++){
            boolean isGood = true;
            for(int next : graph[o]){
                if(h[next]>=h[o]){
                    isGood = false;
                    break;
                }
            }
            res += isGood ? 1 : 0;
        }
        System.out.println(res);
    }
}