#include <bits/stdc++.h>
using namespace std;
bool point[2002][2002];
int N;
int x[3000], y[3000];
const int offset = 1001;
int main() {
  while (scanf("%d", &N) != EOF) {
    memset(point, 0, sizeof point);
    for (int i = 0; i < N; ++i) {
      scanf("%d%d", &x[i], &y[i]);
      point[x[i] + offset][y[i] + offset] = true;
    }
    int tot = 0;
    for (int i = 0; i < N; ++i) {
      for (int j = i + 1; j < N; ++j) {
        if (((x[i] + x[j]) & 1) == 1 || ((y[i] + y[j]) & 1) == 1) continue;
        int mx = (x[i] + x[j]) >> 1;
        int my = (y[i] + y[j]) >> 1;
        if (point[mx + offset][my + offset]) ++tot;
      }
    }
    printf("%d\n", tot);
  }
}
