#include <iostream>
#define MOD 1000000007


using namespace std;

int p[2000][2];
int m[4002][4002];
int vecs[4002][4002];
int n;

int main(){
    cin >> n;
    for(int i=0;i<n;i++){
        cin >> p[i][0] >> p[i][1];
        m[p[i][0]+1000][p[i][1]+1000] = 1;
    }
    int x, y;

    int s = 0;
    for(int i=0;i<n;i++){
        for (int k=-1;k<2;k+=2){
            x = k*(p[i][0] - p[0][0]);
            y = k*(p[i][1] - p[0][1]);
            if (x == 0 && y == 0) continue;
            if (vecs[x+2000][y+2000]) continue;
            vecs[x+2000][y+2000] = 1;

            int good = 1;
            for(int j=0;j<n;j++){
                int x1 = p[j][0] + x + 1000;
                int y1 = p[j][1] + y + 1000;
                int x2 = p[j][0] - x + 1000;
                int y2 = p[j][1] - y + 1000;
                int g1 = x1 >= 0 && y1 >=0 && m[x1][y1];
                int g2 = x2 >= 0 && y2 >=0 && m[x2][y2];
                if (!g1 && !g2) good = 0;
            }
            s += good;
        }
    }

    cout << s << endl;
}