Language: C++

#include <stdio.h>
void quicksort(int M,int N,int a[M][N],int left,int right,int xory);
long long int marea(int M,int N,int a[M][N],int K,int xory);
int main()
{
	int N,K,i;
	long long int area,t;
	scanf("%d %d",&N,&K);
	int a[2][N];
	for(i=0;i<N;i++) scanf("%d %d",&a[0][i],&a[1][i]);
	area=marea(2,N,a,K,0);
	if((t=marea(2,N,a,K,1))<area) area=t;
	printf("%lld",area);
	return 0;
}

void quicksort(int M,int N,int a[M][N],int left,int right,int xory)
{
	if(left<right) {
		int i=left,j=right,tmp1,tmp2,pivot=a[xory][i];
		while(1) {
			while(a[xory][i]<pivot) i++;
			while(pivot<a[xory][j]) j--;
			if(i>=j)break;
			tmp1=a[xory][i];
			tmp2=a[!xory][i];
			a[xory][i]=a[xory][j];
			a[!xory][i]=a[!xory][j];
			a[xory][j]=tmp1;
			a[!xory][j]=tmp2;
			i++;
			j--;
		}
		quicksort(2,N,a,left,i-1,xory);
		quicksort(2,N,a,j+1,right,xory);
	}
}

long long int marea(int M,int N,int a[M][N],int K,int xory)
{
	int i,xa=a[0][0],xi=a[0][0],ya=a[1][0],yi=a[1][0],xb=xa,xj=xi,yb=ya,yj=yi;
	long long int area,t;
	quicksort(2,N,a,0,N-1,xory);
	for(i=0;i<K;i++) {
		if(a[0][i]>xa) {
			xb=xa;
			xa=a[0][i];
		}
		if(a[0][i]<xi) {
			xj=xi;
			xi=a[0][i];
		}
		if(a[1][i]>ya) {
			yb=ya;
			ya=a[1][i];
		}
		if(a[1][i]<yi) {
			yj=yi;
			yi=a[1][i];
		}
	}
	area=(long long)(xa-xi)*(long long)(ya-yi);
	for(i=K;i<N;i++) {
		if((a[0][i-K]==xa)&&(xb!=xa)) xa=xb;
		if((a[0][i-K]==xi)&&(xj!=xi)) xi=xj;
		if((a[1][i-K]==ya)&&(yb!=ya)) ya=yb;
		if((a[1][i-K]==yi)&&(yj!=yi)) yi=yj;
		if(a[0][i]>xa) {
			xb=xa;
			xa=a[0][i];
		}
		if(a[0][i]<xi) {
			xj=xi;
			xi=a[0][i];
		}
		if(a[1][i]>ya) {
			yb=ya;
			ya=a[1][i];
		}
		if(a[1][i]<yi) {
			yj=yi;
			yi=a[1][i];
		}
		if((t=(long long)(xa-xi)*(long long)(ya-yi))<area) area=t;
	}
	return area;
}

Compiler output:
a.cc:2:35: error: use of parameter outside function body before ']' token
    2 | void quicksort(int M,int N,int a[M][N],int left,int right,int xory);
      |                                   ^
a.cc:2:38: error: use of parameter outside function body before ']' token
    2 | void quicksort(int M,int N,int a[M][N],int left,int right,int xory);
      |                                      ^
a.cc:2:39: error: expected ')' before ',' token
    2 | void quicksort(int M,int N,int a[M][N],int left,int right,int xory);
      |               ~                       ^
      |                                       )
a.cc:2:40: error: expected unqualified-id before 'int'
    2 | void quicksort(int M,int N,int a[M][N],int left,int right,int xory);
      |                                        ^~~
a.cc:3:40: error: use of parameter outside function body before ']' token
    3 | long long int marea(int M,int N,int a[M][N],int K,int xory);
      |                                        ^
a.cc:3:43: error: use of parameter outside function body before ']' token
    3 | long long int marea(int M,int N,int a[M][N],int K,int xory);
      |                                           ^
a.cc:3:44: error: expected ')' before ',' token
    3 | long long int marea(int M,int N,int a[M][N],int K,int xory);
      |                    ~                       ^
      |                                            )
a.cc:3:45: error: expected unqualified-id before 'int'
    3 | long long int marea(int M,int N,int a[M][N],int K,int xory);
      |                                             ^~~
a.cc:17:35: error: use of parameter outside function body before ']' token
   17 | void quicksort(int M,int N,int a[M][N],int left,int right,int xory)
      |                                   ^
a.cc:17:38: error: use of parameter outside function body before ']' token
   17 | void quicksort(int M,int N,int a[M][N],int left,int right,int xory)
      |                                      ^
a.cc:17:39: error: expected ')' before ',' token
   17 | void quicksort(int M,int N,int a[M][N],int left,int right,int xory)
      |               ~                       ^
      |                                       )
a.cc:17:40: error: expected unqualified-id before 'int'
   17 | void quicksort(int M,int N,int a[M][N],int left,int right,int xory)
      |                                        ^~~
a.cc:39:40: error: use of parameter outside function body before ']' token
   39 | long long int marea(int M,int N,int a[M][N],int K,int xory)
      |                                        ^
a.cc:39:43: error: use of parameter outside function body before ']' token
   39 | long long int marea(int M,int N,int a[M][N],int K,int xory)
      |                                           ^
a.cc:39:44: error: expected ')' before ',' token
   39 | long long int marea(int M,int N,int a[M][N],int K,int xory)
      |                    ~                       ^
      |                                            )
a.cc:39:45: error: expected unqualified-id before 'int'
   39 | long long int marea(int M,int N,int a[M][N],int K,int xory)
      |                                             ^~~