#include <iostream>
#include <iomanip>
#include <sstream>
#include <vector>
#include <string>
#include <set>
#include <unordered_set>
#include <map>
#include <unordered_map>
#include <stack>
#include <queue>
#include <deque>
#include <algorithm>
#include <functional>
#include <iterator>
#include <limits>
#include <numeric>
#include <utility>
#include <cmath>
#include <cassert>
#include <cstdio>

using namespace std; using namespace placeholders;

using LL = long long;
using ULL = unsigned long long;
using VI = vector< int >;
using VVI = vector< vector< int > >;
using VS = vector< string >;
using SS = stringstream;
using PII = pair< int, int >;
using VPII = vector< pair< int, int > >;
template < typename T = int > using VT = vector< T >;
template < typename T = int > using VVT = vector< vector< T > >;
template < typename T = int > using LIM = numeric_limits< T >;

template < typename T > inline istream& operator>>( istream &s, vector< T > &v ){ for ( T &t : v ) { s >> t; } return s; }
template < typename T > inline ostream& operator<<( ostream &s, const vector< T > &v ){ for ( int i = 0; i < int( v.size() ); ++i ){ s << ( " " + !i ) << v[i]; } return s; }
template < typename T > inline T fromString( const string &s ) { T res; istringstream iss( s ); iss >> res; return res; };
template < typename T > inline string toString( const T &a ) { ostringstream oss; oss << a; return oss.str(); };

#define REP2( i, n ) REP3( i, 0, n )
#define REP3( i, m, n ) for ( int i = ( int )( m ); i < ( int )( n ); ++i )
#define GET_REP( a, b, c, F, ... ) F
#define REP( ... ) GET_REP( __VA_ARGS__, REP3, REP2 )( __VA_ARGS__ )
#define FOR( e, c ) for ( auto &e : c )
#define ALL( c ) ( c ).begin(), ( c ).end()
#define AALL( a, t ) ( t* )a, ( t* )a + sizeof( a ) / sizeof( t )
#define DRANGE( c, p ) ( c ).begin(), ( c ).begin() + p, ( c ).end()

#define SZ( v ) ( (int)( v ).size() )
#define PB push_back
#define EM emplace
#define EB emplace_back
#define BI back_inserter

#define EXIST( c, e ) ( ( c ).find( e ) != ( c ).end() )

#define MP make_pair
#define fst first
#define snd second

#define DUMP( x ) cerr << #x << " = " << ( x ) << endl

LL sqdist( const PII &p, const PII &q )
{
	const LL dy = p.fst - q.fst, dx = p.snd - q.snd;
	return dy * dy + dx * dx;
}

int main()
{
	cin.tie( 0 );
	ios::sync_with_stdio( false );

	VVT< VPII > buckets( 1024, VT< VPII >( 1024 ) );

	int N;
// 	cin >> N;
	scanf( "%d", &N );

	REP( i, N )
	{
		int x, y;
// 		cin >> x >> y;
		scanf( "%d %d", &x, &y );

		const int by = y / 1000 + 1, bx = x / 1000 + 1;

		const PII p( y, x );

		bool ok = true;
		REP( dy, -1, 2 )
		{
			REP( dx, -1, 2 )
			{
				FOR( q, buckets[ by + dy ][ bx + dx ] )
				{
					ok &= 20 * 20 <= sqdist( p, q );
				}
			}
		}

		if ( ok )
		{
			buckets[ by ][ bx ].PB( p );
		}
	}

	int res = 0;
	FOR( row, buckets )
	{
		FOR( ps, row )
		{
			res += SZ( ps );
		}
	}
// 	cout << res << endl;
	printf( "%d\n", res );


	return 0;
}