#include <stdio.h>

#define	CMAX	(100000)

#define WMAX	(32)
#define	HMAX	(32)

int field[HMAX+2][WMAX+2][10000];
int fCnt[HMAX+2][WMAX+2];

int coin[CMAX+2];

int main(void){
	int i,j,k,n;
	int cCnt=0;
	
	scanf("%d", &n);
	
	for(i=0;i<n;i++){
		int nx, ny;
		scanf("%d %d", &nx, &ny);
		coin[i] = nx*100000+ny;
	}
	
	for(i=0;i<n;i++){
		int noHit=1;
		int nx, ny;
		int px, py;
		
		nx = coin[i] / 100000;
		ny = coin[i] % 100000;
		
		px = nx/(20000/WMAX);
		py = ny/(20000/HMAX);
		
//		printf("for i  %d %d %d %d %d\n", i, nx, ny, px, py);
//		printf("for ii  px=%d/(20000/%d) , py=%d/(20000/%d)\n", nx,WMAX, ny, HMAX);
		
		for(j=-1;j<=1;j++){
			for(k=-1;k<=1;k++){
				int s;
				int fx = px+k;
				int fy = py+j;
				
				
				if(fx < 0 || WMAX < fx){continue;}
				if(fy < 0 || HMAX < fy){continue;}
				
//				printf("ff %d %d %d %d %d\n", nx, ny, fx, fy, fCnt[fy][fx]);
				
				for(s=0;s<fCnt[fy][fx];s++){
					int tx = field[fy][fx][s] / 100000;
					int ty = field[fy][fx][s] % 100000;
					int len = (nx-tx)*(nx-tx)+(ny-ty)*(ny-ty);
					
					if( len < 20*20){
						noHit = 0;
						j=k=10;
						break;
					}
				}
			}
		}
		
		if(noHit == 1){
			field[py][px][fCnt[py][px]] = nx*100000+ny;
			fCnt[py][px] += 1;
			
			cCnt += 1;
			
//			printf("Add px[%d], py[%d], fCnt[py][px]=[%d]\n", px, py, fCnt[py][px]);
		}
	}
	
	printf("%d\n", cCnt);
	return 0;
}