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: Runtime Error)

import java.util.*;

public class Main {
    Scanner in = new Scanner(System.in);

    public static void main(String[] args) {
        new Main().solve();
    }

    void solve() {
        int n = in.nextInt();
        int m = in.nextInt();

        int[] obs = new int[n + 1];
        for (int i = 1; i < n; i++) obs[i] = in.nextInt();

        Map<Integer, List<Integer>> map = new HashMap<>();

        for (int i = 0; i < m; i++) {
            int x = in.nextInt();
            int y = in.nextInt();
            if (map.containsKey(x)) {
                List<Integer> list = map.get(x);
                list.add(y);
                map.put(x, list);
            } else map.put(x, new ArrayList<>(y));

            if (map.containsKey(y)) {
                List<Integer> list = map.get(y);
                list.add(x);
                map.put(y, list);
            } else map.put(y, new ArrayList<>(x));
        }

        int count = 0;
        for (Integer key : map.keySet()) {
            boolean x = true;
            for (Integer nums : map.get(key)) {
                if(obs[key] > obs[nums]) {
                    x = false;
                    break;
                }
            }
            if(x) count++;
        }
        System.out.println(count);
    }
}