#include <bits/stdc++.h> using namespace std; using lint = long long int; using P = pair<int, int>; using PL = pair<lint, lint>; #define FOR(i, begin, end) for(int i=(begin),i##_end_=(end);i<i##_end_;i++) #define IFOR(i, begin, end) for(int i=(end)-1,i##_begin_=(begin);i>=i##_begin_;i--) #define REP(i, n) FOR(i,0,n) #define IREP(i, n) IFOR(i,0,n) #define ALL(a) (a).begin(),(a).end() constexpr int MOD = 1000000007; constexpr lint B1 = 1532834020; constexpr lint M1 = 2147482409; constexpr lint B2 = 1388622299; constexpr lint M2 = 2147478017; constexpr int INF = 2147483647; void yes(bool expr) {cout << (expr ? "Yes" : "No") << "\n";} template<class T>void chmax(T &a, const T &b) { if (a<b) a=b; } template<class T>void chmin(T &a, const T &b) { if (b<a) a=b; } struct Dist {lint d, u, v;}; int main() { ios::sync_with_stdio(false); cin.tie(0); cout.tie(0); int N; cin >> N; vector<lint> x(N), y(N); REP(i, N) cin >> x[i] >> y[i]; vector<Dist> d; REP(i, N) FOR(j, i+1, N) d.push_back(Dist{(x[i]-x[j])*(x[i]-x[j]) + (y[i]-y[j])*(y[i]-y[j]), i, j}); sort(ALL(d), [](auto const &a, auto const &b) { return a.d < b.d; }); vector<bool> existed(N, true); int ans = 0; REP(i, d.size()) { if(d[i].u == 0) { if(existed[d[i].v]) { ans++; existed[d[i].v] = false; } } else if(existed[d[i].u] && existed[d[i].v]){ existed[d[i].u] = false; existed[d[i].v] = false; } } cout << ans << endl; }