#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define int long long
#define maxn 500005
#define mi LLONG_MIN
#define ma LLONG_MAX
#define mod 1000000007
#define pb push_back
#define S second
#define F first
void solve() {
int n;
cin >> n;
int md = 2 * n, mx = 0, mad = 1;
vector<pair<int, int>> a(n), b(n * 2);
vector<int> cnt(2 * n, 0);
for (int i = 0; i < n; i++) {
int x, y;
cin >> x >> y;
if ((x + y) % 2)
if (mx < ++cnt[(x + y) % md]) mad = (x + y) % md;
a[i] = {x, y};
b[x] = {i, y};
b[y] = {i, x};
}
int ans = n - cnt[mad];
// x + y == mad ---> y = mad - x
struct str {
int p, s, e;
};
vector<str> answ;
vector<int> used(2 * n, 0);
for (int i = 0; i < 2 * n; i++) {
if (used[i]) continue;
int cur = i;
int x = (mad - cur + md) % md;
while (!used[x] && b[cur].S != x) {
answ.pb({b[cur].F, b[cur].S, x});
used[cur] = 1;
used[x] = 1;
cur = b[x].S;
x = (mad - cur + md) % md;
}
}
cout << ans << "\n";
for (auto it : answ) cout << it.p << " " << it.s << " " << it.e << "\n";
}
int32_t main() {
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int t = 1;
// cin >> t;
while (t--) solve();
}
