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# (Mono-mcs 6.8.0.105) (judge verdict: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;
class abc166_c{
  public static void Main(){
    String[] str = Console.ReadLine().Split(' ');
    int n = int.Parse(str[0]);
    int m = int.Parse(str[1]);
    int[] h = Console.ReadLine().Split(' ').Select(s => int.Parse(s)).ToArray();
    List<int>[] to = new List<int>[n];
    for(int i=0; i<n; i++){
      to[i] = new List<int>();
    }
    for(int i=0; i<m; i++){
      int[] ab = Console.ReadLine().Split(' ').Select(s => int.Parse(s)).ToArray();
      to[ab[0]-1].Add(ab[1]-1);
      to[ab[1]-1].Add(ab[0]-1);
    }
    int count = 0;
    bool flag = true;
    for(int i=0; i<to.Length; i++){
      List<int> t = to[i];
      flag = true;
      for(int j=0; j<t.Count; j++){
        if(h[i] > h[t[j]]){
          flag = false;
          break;
        }
      }
      if(flag && t.Count != 0){
        count++;
      }
    }
    Console.WriteLine(count);
  }
}