// #pragma GCC optimize("Ofast")
// #pragma GCC target("avx,avx2,fma,popcnt")
#include <bits/stdc++.h>
using namespace std;
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define emb emplace_back
#define pb push_back
#define mt make_tuple
#define fi first
#define se second
#define uniq(x) (x).erase(unique(all(x)), x.end())
#define BIT(x, i) (((x)>>(i))&1)
#define MASK(i) (1LL<<(i))
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<long long> vl;
template<typename T1, typename T2> bool mini(T1 &a, T2 b)
{if(a>b) a=b; else return 0; return 1;}
template<typename T1, typename T2> bool maxi(T1 &a, T2 b)
{if(a<b) a=b; else return 0; return 1;}
const int mxN = 3e3 + 7;
const int md = 1e9 + 7;
const int inf = 1e9 + 7;
struct Angle {
int x, y;
int t;
Angle(int x, int y, int t=0) : x(x), y(y), t(t) {}
Angle operator-(Angle b) const { return {x-b.x, y-b.y, t}; }
int half() const {
assert(x || y);
return y < 0 || (y == 0 && x < 0);
}
Angle t90() const { return {-y, x, t + (half() && x >= 0)}; }
Angle t180() const { return {-x, -y, t + half()}; }
Angle t360() const { return {x, y, t + 1}; }
};
bool operator<=(Angle a, Angle b) {
// add a.dist2() and b.dist2() to also compare distances
return make_tuple(a.t, a.half(), a.y * (ll)b.x) <=
make_tuple(b.t, b.half(), a.x * (ll)b.y);
}
bool operator<(Angle a, Angle b) {
// add a.dist2() and b.dist2() to also compare distances
return make_tuple(a.t, a.half(), a.y * (ll)b.x) <
make_tuple(b.t, b.half(), a.x * (ll)b.y);
}
// Given two points, this calculates the smallest angle between
// them, i.e., the angle that covers the defined line segment.
pair<Angle, Angle> segmentAngles(Angle a, Angle b) {
if (b < a) swap(a, b);
return (b < a.t180() ?
make_pair(a, b) : make_pair(b, a.t360()));
}
Angle operator+(Angle a, Angle b) { // point a + vector b
Angle r(a.x + b.x, a.y + b.y, a.t);
if (a.t180() < r) r.t--;
return r.t180() < a ? r.t360() : r;
}
Angle angleDiff(Angle a, Angle b) { // angle b - angle a
int tu = b.t - a.t; a.t = b.t;
return {a.x*b.x + a.y*b.y, a.x*b.y - a.y*b.x, tu - (b < a)};
}
int dp[mxN][mxN][2];
pii trace[mxN][mxN][2];
int main() {
ios_base::sync_with_stdio(0); cin.tie(0);
int n;
cin >> n;
vector<pii> a(n + 7);
for (int i = 1; i <= n; i++) {
cin >> a[i].fi >> a[i].se;
if (i > 1 && a[1].se > a[i].se) {
swap(a[1], a[i]);
}
}
auto cross = [&](pii a, pii b) {
return 1LL * a.fi * b.se - 1LL * a.se * b.fi;
};
auto cross3 = [&](pii a, pii b, pii c) {
pii t1 = make_pair(b.fi - a.fi, b.se - a.se);
pii t2 = make_pair(c.fi - a.fi, c.se - a.se);
return cross(t1, t2);
};
auto sq = [&](pii a, pii b) {
return 1LL * (a.fi - b.fi) * (a.fi - b.fi) + 1LL * (a.se - b.se) * (a.se - b.se);
};
sort (a.begin() + 2, a.begin() + 1 + n, [&](pii x, pii y){
ll temp = cross3(a[1], x, y);
if (temp != 0) return temp > 0;
return sq(a[1], x) < sq(a[1], y);
});
// for (int i = 1; i <= n; i++) {
// for (int j = 1; j <= n; j++) {
// if (j < i) lef[i].pb(make_pair(Angle(a[j].fi - a[i].fi, a[j].se - a[i].se, 0), j));
// if (j > i) rig[i].pb(make_pair(Angle(a[j].fi - a[i].fi, a[j].se - a[i].se, 0), j));
// }
// sort(all(lef[i]));
// sort(all(rig[i]));
// }
int res = dp[0][0][0];
array<int, 3> path = {1, 1, 1};
for (int i = 2; i <= n; i++) dp[i][1][0] = 2;
for (int i = 2; i <= n; i++) {
vector<int> lef, rig;
for (int j = 1; j <= n; j++) {
if (j < i) lef.pb(j);
if (j > i) rig.pb(j);
}
sort(all(lef), [&](int &x, int &y){
return Angle(a[x].fi - a[i].fi, a[x].se - a[i].se) < Angle(a[y].fi - a[i].fi, a[y].se - a[i].se);
});
sort(all(rig), [&](int &x, int &y){
return Angle(a[x].fi - a[i].fi, a[x].se - a[i].se) < Angle(a[y].fi - a[i].fi, a[y].se - a[i].se);
});
for (int cur = 0; cur < 2; cur++) {
int l = 0, r = 0;
deque<pii> dq;
for (auto it : rig) {
if (cross3(a[1], a[i], a[it]) == 0) continue;
while (l < sz(lef) + sz(lef)) {
int idx = (l < sz(lef) ? lef[l] : lef[l - sz(lef)]);
Angle t1(a[idx].fi - a[i].fi, a[idx].se - a[i].se);
if (l >= sz(lef)) t1 = t1.t360();
Angle t2(a[it].fi - a[i].fi, a[it].se - a[i].se);
if (cur == 1) t2 = t2.t180();
if (t1 <= t2) {
++l;
while (sz(dq) && dq.front().se < l) dq.pop_front();
} else {
break;
}
}
r = max(l, r);
while (r < sz(lef) + sz(lef)) {
int idx = (r < sz(lef) ? lef[r] : lef[r - sz(lef)]);
Angle t1(a[idx].fi - a[i].fi, a[idx].se - a[i].se);
if (r >= sz(lef)) t1 = t1.t360();
Angle t2(a[it].fi - a[i].fi, a[it].se - a[i].se);
if (cur == 1) t2 = t2.t360();
else t2 = t2.t180();
if (t1 < t2) {
int val;
if (r < sz(lef)) val = dp[i][lef[r]][cur];
else val = dp[i][lef[r - sz(lef)]][cur];
if (val > 0) {
while (sz(dq) && dq.back().fi < val) dq.pop_back();
dq.push_back(make_pair(val, r));
}
++r;
} else {
break;
}
}
assert(l <= r);
if (sz(dq)) {
int idx;
if (dq.front().se < sz(lef)) idx = lef[dq.front().se];
else idx = lef[dq.front().se - sz(lef)];
if (maxi(dp[it][i][cur ^ 1], dq.front().fi + 1)) {
trace[it][i][cur ^ 1] = {i, idx};
}
}
}
}
}
for (int i = 1; i <= n; i++) {
for (int j = 1; j < i; j++) {
if (maxi(res, dp[i][j][0])) {
path = {i, j, 0};
}
}
}
// cout << dp[2][1][0] << ' ' << dp[3][2][1] << ' ' << dp[4][3][0] << ' ' << dp[5][4][1] << '\n';
if (res >= 4) {
vector<int> ans;
ans.pb(path[0]);
ans.pb(path[1]);
while (path[0] != 0 && path[1] != 0) {
pii temp = trace[path[0]][path[1]][path[2]];
path[0] = temp.fi;
path[1] = temp.se;
path[2] ^= 1;
if (path[1] > 0) ans.pb(path[1]);
}
reverse(all(ans));
cout << sz(ans) << '\n';
for (auto it : ans) cout << a[it].fi << ' ' << a[it].se << '\n';
} else {
cout << 0 << '\n';
}
return 0;
}
