#include <bits/stdc++.h>
#define f first
#define s second
#define int long long
using namespace std;
void solve(){
int n;
cin>>n;
vector <pair <int, int> > p(n);
vector <int> tp(2*n);
for(pair <int, int> &j:p){
cin>>j.f>>j.s;
}
vector <int> tm(n, n);
for(int i=0; i<n; ++i){
tp[p[i].f]=i;
tp[p[i].s]=i;
}
for(int i=0; i<n; ++i){
if(0==((2*n+2*n-p[i].s-1-p[i].f)%(2*n))&1){
--tm[((2*n+2*n-p[i].s-1-p[i].f)%(2*n))/2];
}
}
int mn=0;
for(int i=0; i<n; ++i){
if(tm[i]<tm[mn]){
mn=i;
}
}
cout<<tm[mn]<<"\n";
for(int i=0; i<n; ++i){
if(p[i].f==(2*n+2*n-p[i].s-1-2*mn)%(2*n)){
continue;
}
int ap=p[i].f;
while(ap!=(2*n+2*n-p[tp[ap]].s-1-2*mn)%(2*n)){
cout<<tp[ap]<<" "<<p[tp[ap]].s<<" ";
int np=(2*n+2*n-1-2*mn-ap)%(2*n);
p[tp[ap]].s=np;
cout<<np<<"\n";
if(p[tp[np]].f==np){
int aux=p[tp[np]].f;
p[tp[np]].f=p[tp[np]].s;
p[tp[np]].s=aux;
}
np=p[tp[np]].f;
tp[(2*n+2*n-1-2*mn-ap)%(2*n)]=tp[ap];
ap=np;
}
}
return;
}
signed main(){
int T=1;
//cin>>T;
while(T--){
solve();
}
return 0;
}
