#include<bits/stdc++.h>
using namespace std;
vector<pair<long long,long long>> haha(1);
vector<pair<long long,long long>> ans(0);
long long s(pair<long long,long long> a, pair<long long,long long> b) {
return (a.first+b.first)*(b.second-a.second);
}
long long ori(pair<long long,long long> a, pair<long long,long long> b, pair<long long,long long> c) {
return s(a,b)+s(b,c)+s(c,a);
}
bool compa(pair<pair<long long,long long>,long long> a, pair<pair<long long,long long>,long long> b) {
long long x1 = a.first.first,x2 = b.first.first;
long long y1 = a.first.second,y2 = b.first.second;
if(y1*y2 < 0) {
if(y1 > 0) {
return true;
}
else {
return false;
}
}
if(y1*y2 == 0) {
if(y1 == 0 && y2 == 0) {
if(x1 > 0) {
return true;
}
else {
return false;
}
}
if(y1 == 0) {
if(x1 > 0 || y2 < 0) {
return true;
}
else {
return false;
}
}
else {
if(x2 > 0 || y1 < 0) {
return false;
}
else {
return true;
}
}
}
return (x1*y2 > x2*y1);
}
void dude(vector<long long> wut) {
if(wut.size() == 2) {
ans.push_back({wut[0],wut[1]});
return;
}
pair<pair<long long,long long>,long long> sm = {{LLONG_MAX,LLONG_MAX},0};
for(long long i = 0; i < wut.size(); i++) {
sm = min({{haha[wut[i]].second,haha[wut[i]].first},i},sm);
}
sm = {{sm.first.second,sm.first.first},sm.second};
vector<pair<pair<long long,long long>,long long>> idk(0);
for(long long i = 0; i < wut.size(); i++) {
if(i != sm.second) {
long long x = haha[wut[i]].first-sm.first.first;
long long y = haha[wut[i]].second-sm.first.second;
idk.push_back({{x,y},wut[i]});
}
}
sort(idk.begin(),idk.end(),compa);
long long p = -1;
for(long long i = 1; i < idk.size()-1; i++) {
if(ori(haha[idk[i-1].second],haha[idk[i].second],haha[idk[i+1].second]) < 0) {
p = idk[i].second;
}
}
if(p == -1) {
ans.push_back({wut[sm.second],idk[0].second});
ans.push_back({wut[sm.second],idk[idk.size()-1].second});
for(long long i = 1; i < idk.size(); i++) {
ans.push_back({idk[i].second,idk[i-1].second});
}
return;
}
vector<pair<pair<long long,long long>,long long>> yo(0);
for(long long v: wut) {
if(v != p) {
long long x = haha[v].first-haha[p].first,y = haha[v].second-haha[p].second;
yo.push_back({{x,y},v});
yo.push_back({{-x,-y},-v});
}
}
sort(yo.begin(),yo.end(),compa);
vector<vector<long long>> banana(0);
vector<long long> wow(0);
for(long long i = 0; i < yo.size(); i++) {
if(yo[i].second > 0) {
wow.push_back(yo[i].second);
}
else {
if(wow.size() > 0) {
banana.push_back(wow);
}
wow.clear();
}
}
if(banana.size()%2 == 1) {
for(long long v: wow) {
banana[0].push_back(v);
}
}
else {
banana.push_back(wow);
}
for(vector<long long> w: banana) {
w.push_back(p);
dude(w);
}
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
long long n,a,b;
cin >> n;
for(long long i = 0; i < n; i++) {
cin >> a >> b;
haha.push_back({a,b});
}
vector<long long> wut(0);
for(long long i = 1; i <= n; i++) {
wut.push_back(i);
}
dude(wut);
cout << ans.size() << "\n";
for(pair<long long,long long> v: ans) {
cout << v.first << " " << v.second << "\n";
}
return 0;
}
