#include <bits/stdc++.h>
using namespace std;
int N;
vector<int> ct;
int mx_ind = -1;
vector<bool> visited;
vector<int> nxt;
vector<int> v;
void dfs(int node)
{
vector<int> order;
visited[node] = true;
while (true)
{
order.emplace_back(node);
node = mx_ind - node;
if (node < 0) node += N * 2;
visited[node] = true;
order.emplace_back(node);
node = nxt[node];
if (visited[node]) break;
visited[node] = true;
}
// for (auto i : order) cout << i << ' ';
for (int i = 1; i < (int)order.size(); i += 2)
{
cout << v[order[i]] + 1 << ' ' << nxt[order[i]] << ' ' << order[i - 1] << '\n';
}
}
int main()
{
cin >> N;
v.resize(N * 2);
ct.resize(N * 2);
nxt.resize(N * 2);
visited.resize(N * 2);
for (int i = 0; i < N; i++)
{
int x, y;
cin >> x >> y;
if (x > y) swap(x, y);
nxt[x] = y, nxt[y] = x;
v[x] = i, v[y] = i;
ct[(x + y) % (N * 2)]++;
}
int mx = -1;
for (int i = 0; i < N * 2; i++)
{
if (ct[i] > mx) {mx = ct[i], mx_ind = i;}
}
int ans = 0;
for (int i = 0; i < N * 2; i++)
{
if ((i + nxt[i] - mx_ind) % (N * 2) == 0) visited[i] = true;
else ans++;
}
cout << ans / 2 << '\n';
for (int i = 0; i < N * 2; i++)
{
if (!visited[i]) dfs(i);
}
return 0;
}
