#include using namespace std; #define SZ(x) (int)(x.size()) #define REP(i, n) for(int i=0;i<(n);++i) #define FOR(i, a, b) for(int i=(a);i<(b);++i) #define RREP(i, n) for(int i=(int)(n)-1;i>=0;--i) #define RFOR(i, a, b) for(int i=(int)(b)-1;i>=(a);--i) #define ALL(a) a.begin(),a.end() #define DUMP(x) cerr<<#x<<" = "<<(x)<; using vvi = vector; using vll = vector; using vvll = vector; using P = pair; const double EPS = 1e-8; const ll MOD = 1000000007; const int INF = INT_MAX / 2; const ll LINF = LLONG_MAX / 2; template bool chmax(T1 &a, const T2 &b) { if (a < b) { a = b; return true; } return false; } template bool chmin(T1 &a, const T2 &b) { if (a > b) { a = b; return true; } return false; } template ostream &operator<<(ostream &os, const map &mp); template ostream &operator<<(ostream &os, const vector &v); template ostream &operator<<(ostream &os, const pair &p) { os << "(" << p.first << ":" << p.second << ")"; return os; } template ostream &operator<<(ostream &os, const map &mp) { os << "{"; int a = 0; for (auto &tp : mp) { if (a) os << ", "; a = 1; os << tp; } return os << "}"; } template ostream &operator<<(ostream &os, const vector &v) { os << "["; REP(i, SZ(v)) { if (i) os << ", "; os << v[i]; } return os << "]"; } using Real = double; const Real PI = acos(-1); using Point = complex; namespace std { bool operator<(const Point& a, const Point& b) { if (a.real() == b.real()) return a.imag() < b.imag(); return a.real() < b.real(); } } struct Line { Point a, b; Line() {} Line(const Point& a, const Point& b) : a(a), b(b) {} friend ostream& operator<<(ostream& os, const Line& l) { return os << "[" << l.a << "," << l.b << "]"; } }; struct Segment : Line { Segment() = default; Segment(const Point& a, const Point& b) : Line(a, b) {} }; inline bool eq(Real a, Real b) { return abs(b - a) < EPS; } Real radian_to_degree(Real r) { return r * 180.0 / PI; } Real degree_to_radian(Real d) { return d * PI / 180.0; } Point rotate(const Point &p, Real theta) { return p * polar((Real)1.0, theta); } Real cross(const Point& a, const Point& b) { return a.real() * b.imag() - a.imag() * b.real(); } Real dot(const Point& a, const Point& b) { return a.real() * b.real() + a.imag() * b.imag(); } Point projection(const Line& l, const Point& p) { Real A = dot(l.b - l.a, p - l.a), B = dot(l.a - l.b, p - l.b); return (A * l.b + B * l.a) / (A + B); } bool parallel(const Line& l1, const Line& l2) { return eq(cross(l1.a - l1.b, l2.a - l2.b), 0.0); } bool orthogonal(const Line& l1, const Line& l2) { return eq(dot(l1.a - l1.b, l2.a - l2.b), 0.0); } const int COUNTER_CLOCKWISE = 1, CLOCKWISE = -1, ONLINE_BACK = 2, ONLINE_FRONT = -2, ON_SEGMENT = 0; int ccw(const Point& a, Point b, Point c) { b = b - a, c = c - a; if (cross(b, c) > EPS) return COUNTER_CLOCKWISE; if (cross(b, c) < -EPS) return CLOCKWISE; if (dot(b, c) < 0) return ONLINE_BACK; if (norm(b) < norm(c)) return ONLINE_FRONT; return ON_SEGMENT; } bool intersected(const Line& l, const Point& p) { return abs(ccw(l.a, l.b, p)) != 1; } bool intersected(const Segment& s, const Point& p) { return ccw(s.a, s.b, p) == 0; } bool intersected(const Line& l, const Segment& s) { return cross(l.b - l.a, s.a - l.a) * cross(l.b - l.a, s.b - l.a) < EPS; } bool intersected(const Segment& s1, const Segment& s2) { return ccw(s1.a, s1.b, s2.a) * ccw(s1.a, s1.b, s2.b) <= 0 and ccw(s2.a, s2.b, s1.a) * ccw(s2.a, s2.b, s1.b) <= 0; } Real distance(const Line& l, const Point& p) { return abs(p - projection(l, p)); } Real distance(const Segment& s, const Point& p) { Point r = projection(s, p); if (intersected(s, r)) return abs(r - p); return min(abs(s.a - p), abs(s.b - p)); } Real distance(const Line &l, const Segment &s) { if (intersected(l, s)) return 0; return min(distance(l, s.a), distance(l, s.b)); } Real distance(const Segment& s1, const Segment& s2) { if (intersected(s1, s2)) return 0.0; return min({ distance(s1, s2.a), distance(s1, s2.b), distance(s2, s1.a), distance(s2, s1.b) }); } Point crosspoint(const Line& l1, const Line& l2) { Real A = cross(l2.a - l1.a, l2.b - l1.a), B = cross(l2.b - l1.b, l2.a - l1.b); return (A * l1.b + B * l1.a) / (A + B); } int main() { cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(10); int n; cin >> n; vector p(n); REP(i, n) { double x, y; cin >> x >> y; p[i] = {x, y}; } int ans = 0; REP(i, n) { FOR(j, i+1, n) { int cnt = 2; REP(k, n) { if (i == k or j == k) continue; if (abs(ccw(p[i], p[j], p[k])) != 1) ++cnt; } chmax(ans, cnt); } } cout << ans << endl; return 0; }