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 (GCC 9.2.1) (judge verdict: Wrong Answer)

#include <stdio.h>

int main(void)
{
  long n, m;

  scanf("%ld%ld", &n, &m);

  long long h[n];

  for (long i = 0; i < n; i++)
    scanf("%lld", &h[i]);

  long ab[m][2];

  for (long i = 0; i < m; i++)
    for (long j = 0; j < 2; j++)
      scanf("%ld", &ab[i][j]);

  /*M本の道に従って計算*/
  long ans = 0, hh[n]; /* <- pear よりhigh なら++*/
  for (long i = 0; i < n; i++)
    hh[i] = 0;

  for (long i = 0; i < m; i++) {
    if (h[ab[i][0]] > h[ab[i][1]]) hh[ab[i][0]]++;
    else if(h[ab[i][0]] < h[ab[i][1]])  hh[ab[i][1]]++;
  }

  for (long i = 0; i < n; i++)
    if (hh[i] != 0) ans++;
    
  printf("%ld\n", ans);

  return 0;
}