func_code_string: #include<bits/stdc++.h>   using namespace std;   typedef long long ll;   typedef pair<int,int> PII;   const int maxn=111111,mod=998244353;   const double PI=3.141592653589793;   #define MP make_pair   #define PB push_back   #define lson o<<1,l,mid   #define rson o<<1|1,mid+1,r   #define FOR(i,a,b) for(int i=(a);i<=(b);i++)   #define ROF(i,a,b) for(int i=(a);i>=(b);i--)   #define MEM(x,v) memset(x,v,sizeof(x))   inline ll read(){    char ch=getchar();ll x=0,f=0;    while(ch< 0  || ch> 9 ) f|=ch== - ,ch=getchar();    while(ch>= 0  && ch<= 9 ) x=x*10+ch- 0 ,ch=getchar();    return f?-x:x;   }   inline int qpow(int a,int b){    int ans=1;    for(;b;b>>=1,a=1ll*a*a%mod) if(b&1) ans=1ll*ans*a%mod;    return ans;   }   int n,at,id[maxn],a[maxn],cnt,ans[maxn][2],al;   bool vis[maxn];   struct point{    int x,y,id;    point operator-(const point &p)const{return (point){x-p.x,y-p.y,id};}    double ang()const{return atan2(y,x);}    bool operator<(const point &p)const{     if(p.id==at) return false;     if(id==at) return true;     return ang()<p.ang();    }   }p[maxn],q[maxn];   inline void add(int x,int y){    ans[++al][0]=x;    ans[al][1]=y;    swap(a[x],a[y]);   }   void dfs(int x){    id[x]=cnt;    if(!id[a[x]]) dfs(a[x]);   }   int main(){    n=read();    FOR(i,1,n) p[i].x=read(),p[i].y=read(),a[i]=read(),p[i].id=i;    FOR(i,1,n) if(i!=a[i]){     if(!at || MP(p[i].x,p[i].y)<MP(p[at].x,p[at].y)) at=i;    }    if(!at) return puts( 0 ),0;    FOR(i,1,n) if(!id[i]) cnt++,dfs(i);    FOR(i,1,n) if(i!=at) p[i]=p[i]-p[at];    sort(p+1,p+n+1);    if(p[n].ang()-p[2].ang()>PI){     ROF(i,n,2) if(p[i].ang()-p[2].ang()<PI){      q[1]=p[1];      FOR(j,i+1,n) q[j-i+1]=p[j];      FOR(j,2,i) q[n-i+j]=p[j];      break;     }    }    else FOR(i,1,n) q[i]=p[i];    vis[id[q[2].id]]=true;    FOR(i,3,n) if(!vis[id[q[i].id]]){     add(q[i].id,q[i-1].id);     vis[id[q[i].id]]=true;    }    while(a[at]!=at) add(a[at],at);    printf( %d n ,al);    FOR(i,1,al) printf( %d %d n ,ans[i][0],ans[i][1]);   }