Language: C

#include <stdio.h>
#define MAX(a,b) ((a) > (b) ? (a) : (b));

int countTree(int a,int b,int c,int d,int e[][]);

int main(){
	int N;
	int i,j;
	while(1){
		int maxNumber=0;
		scanf("%d",&N); if(N==0) break;
		scanf("%d%d",&W,&H);
		int map[H][W]={};
		for(i=0;i<N;i++){
			scanf("%d%d",&x,&y);
			map[x][y]=1;
		}
		scanf("%d%d",&S,&T);
		for(i=0;i<H-T+1;i++){
			for(j=0;j<W-S+1;j++) maxNumber=MAX(maxNumber,countTree(i,j,S,T,map));
		}
		printf("%d\n",maxNumber);
	}
}

int countTree(int a,int b,int c,int d,int e[][]){
	int k,l;
	int countSum=0;
	for(k=0;k<a+c;i++){
		for(l=0;l<b+d;l++){
			if(e[k][l]==1) countSum++;
		}
	}
	return countSum;
}

Compiler output:
main.c:4:43: error: array type has incomplete element type 'int[]'
    4 | int countTree(int a,int b,int c,int d,int e[][]);
      |                                           ^
main.c:4:43: note: declaration of 'e' as multidimensional array must have bounds for all dimensions except the first
main.c: In function 'main':
main.c:12:31: error: 'W' undeclared (first use in this function)
   12 |                 scanf("%d%d",&W,&H);
      |                               ^
main.c:12:31: note: each undeclared identifier is reported only once for each function it appears in
main.c:12:34: error: 'H' undeclared (first use in this function)
   12 |                 scanf("%d%d",&W,&H);
      |                                  ^
main.c:15:39: error: 'x' undeclared (first use in this function)
   15 |                         scanf("%d%d",&x,&y);
      |                                       ^
main.c:15:42: error: 'y' undeclared (first use in this function)
   15 |                         scanf("%d%d",&x,&y);
      |                                          ^
main.c:18:31: error: 'S' undeclared (first use in this function)
   18 |                 scanf("%d%d",&S,&T);
      |                               ^
main.c:18:34: error: 'T' undeclared (first use in this function)
   18 |                 scanf("%d%d",&S,&T);
      |                                  ^
main.c:20:88: error: type of formal parameter 5 is incomplete
   20 |                         for(j=0;j<W-S+1;j++) maxNumber=MAX(maxNumber,countTree(i,j,S,T,map));
      |                                                                                        ^~~
main.c:2:26: note: in definition of macro 'MAX'
    2 | #define MAX(a,b) ((a) > (b) ? (a) : (b));
      |                          ^
main.c:20:88: error: type of formal parameter 5 is incomplete
   20 |                         for(j=0;j<W-S+1;j++) maxNumber=MAX(maxNumber,countTree(i,j,S,T,map));
      |                                                                                        ^~~
main.c:2:38: note: in definition of macro 'MAX'
    2 | #define MAX(a,b) ((a) > (b) ? (a) : (b));
      |                                      ^
main.c: At top level:
main.c:26:43: error: array type has incomplete element type 'int[]'
   26 | int countTree(int a,int b,int c,int d,int e[][]){
      |                                           ^
main.c:26:43: note: declaration of 'e' as multidimensional array must have bounds for all dimensions except the first
main.c: In function 'countTree':
main.c:29:23: error: 'i' undeclared (first use in this function)
   29 |         for(k=0;k<a+c;i++){
      |                       ^