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: Accepted)

#include <stdio.h>
#include <stdlib.h>
 
typedef long long ll;
typedef struct ways{
    ll A;
    ll B;
}way;

int acmp(const void* left, const void* right){
    if (((way *)left)->A > ((way *)left)->A) return 1;
	else if (((way *)left)->A < ((way *)left)->A) return -1;
	else return 0;
}
 
int main(){
    ll N,M,count,ans;
    ans = 0;
    scanf("%lld %lld",&N,&M);
    ll H[N];
    char flag[N];
    for(ll i = 0;i<N;i++){
        scanf("%lld ",&H[i]);
        flag[i] = 1;
    }
    way w[M];
    for(ll i = 0;i<M;i++) scanf("%lld %lld",&(w[i].A),&(w[i].B));
    qsort(w,M,sizeof(way),acmp);
    for(ll i = 0;i<M;i++){
        if(H[w[i].A-1] < H[w[i].B-1]) flag[w[i].A-1] = 0;
        else if(H[w[i].A-1] > H[w[i].B-1]) flag[w[i].B-1] = 0;
        else {
            flag[w[i].A-1] = 0;
            flag[w[i].B-1] = 0;
        }
    }
    for(ll i = 0;i<N;i++) ans += flag[i];
    printf("%lld\n",ans);
    return 0;
}