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 Ruby (2.7.1) (judge verdict: Accepted)


N,M=gets.chomp.split(" ").map(&:to_i);
H=gets.chomp.split(" ").map(&:to_i);
#line = readlines.split(" ").map(&:to_i)
line = M.times.map { gets.split.map(&:to_i) }
#N = 6
#M = 5
#H=[8,6,9,1,2,1]
#line = [[1,3],[4,2],[4,3],[4,6],[4,6]]
clist=Array.new(N)
i=0
while i<line.length
  if H[line[i][0]-1]>H[line[i][1]-1]
    #H[i][1]番目はない
    clist[line[i][1]-1]="no"
  elsif H[line[i][0]-1]<H[line[i][1]-1]
    #H[i][0]番目はない
    clist[line[i][0]-1]="no"
  elsif H[line[i][0]-1]==H[line[i][1]-1] && clist[line[i][0]-1]="no" 
    clist[line[i][1]-1]="no"
  elsif H[line[i][0]-1]==H[line[i][1]-1] && clist[line[i][1]-1]="no" 
    clist[line[i][0]-1]="no"
  end
  i+=1
end
count = 0

j=0
while j < clist.length
  if clist[j].nil?
    count+=1
  end
  j+=1
end

p count