#include<bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef unsigned u;
typedef vector<int> vi;
typedef pair<int, int> pii;
#define F first;
#define S second;
#define PB push_back;
#define MP make_pair;

bool EQ(double a, double b) {
    return (fabs(a-b) / (a+b) < DBL_EPSILON);
}

int main( ) {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    // code
    int n, x, y, cnt = 0;
    set<pii> spts, vecs;
    int ptsx[1000];
    int ptsy[1000];

    cin >> n;
    for (int i = 0; i < n; i++) {
        cin >> x >> y;
        spts.insert(make_pair(x, y));
        ptsx[i] = x;
        ptsy[i] = y;
    }

    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++ ) {
            if ( ptsx[i] == ptsx[j] and ptsy[i] == ptsy[j] )
                continue;
            pii v = make_pair(ptsx[j] - ptsx[i], ptsy[j] - ptsy[i]);
            if (vecs.count(v) > 0)
                continue;
            vecs.insert(v);
            bool ok = true;

            for (int k = 0; k < n; k++) {
                pii sh1 = make_pair(ptsx[k] + v.first, ptsy[k] + v.second); // na nekoho
                pii sh2 = make_pair(ptsx[k] - v.first, ptsy[k] - v.second); // na me
                if (spts.count(sh1) == 0 and spts.count(sh2) == 0) {
                    ok = false;
                    break;
                }
            }
            if (ok)
                cnt++;
        }
    }
    cout << cnt;

    return 0;
}