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 Go (1.14.1) (judge verdict: Accepted)

package main

import "fmt"

func main() {
	var n, m int
	
	fmt.Scan(&n)
	fmt.Scan(&m)
	
	h := make([]int, n, n)
	b := make(map[int][]int)
	for i := 0; i < n; i++ {
		var tmp int
		fmt.Scan(&tmp)
		h[i] = tmp
	}
	for i := 0; i < m; i++ {
		var tmp1,tmp2 int
		fmt.Scan(&tmp1)
		fmt.Scan(&tmp2)
		tmp1--
		tmp2--
		_, ok1 := b[tmp1]
		if ok1 {
			b[tmp1] = append(b[tmp1], tmp2)
		} else {
			b[tmp1] = []int{tmp2}
		}
		_, ok2 := b[tmp2]
		if ok2 {
			b[tmp2] = append(b[tmp2], tmp1)
		} else {
			b[tmp2] = []int{tmp1}
		}
	}

	answer := 0
	for i := 0; i < n; i++ {
		ok := true
		l := len(b[i])
		if l > 0 {
			for j := 0; j < l; j++ {
				if h[b[i][j]] >= h[i] {
					ok = false
				}
			}
		}
		if ok {
			answer++
		}
	}

	fmt.Println(answer)
}