#include <bits/stdc++.h>
#include <string>
#define REP(i,a,b) for(i=a;i<b;i++)
#define rep(i,n) REP(i,0,n)

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;

#define SQR(X) ((X)*(X))
int itien[20020][20020];
/*          y      x          */
int main() {
  int i,j,k;
  int N;
  int sum = 0;
  cin >> N;
  rep(i,N) {
	int y,x;
	bool valid = true;
	scanf("%d %d",&x,&y);
	for(j=-19;j<20;j++) {
	  if(y+j < 0) continue;
	  for(k=-19;k<20;k++) {
		if(x+k < 0) continue;
		if(itien[y+j][x+k] == 0) continue;
		else if(400 > SQR(j) + SQR(k) ) valid = false;
	  }
	}
	if(valid) {
	  itien[y][x] = 1; sum++;
	  // printf("i = %d\n",i);
	}
  }
  cout << sum << endl;
  return 0;
}