#include <bits/stdc++.h>
using namespace std;
const int MOD = (int)1e9 + 7;
const int FFTMOD = 119 << 23 | 1;
const int INF = (int)1e9 + 23111992;
const long long LINF = (long long)1e18 + 23111992;
const long double PI = acos((long double)-1);
const long double EPS = 1e-9;
inline long long gcd(long long a, long long b) {
  long long r;
  while (b) {
    r = a % b;
    a = b;
    b = r;
  }
  return a;
}
inline long long lcm(long long a, long long b) { return a / gcd(a, b) * b; }
inline long long fpow(long long n, long long k, int p = MOD) {
  long long r = 1;
  for (; k; k >>= 1) {
    if (k & 1) r = r * n % p;
    n = n * n % p;
  }
  return r;
}
template <class T>
inline int chkmin(T& a, const T& val) {
  return val < a ? a = val, 1 : 0;
}
template <class T>
inline int chkmax(T& a, const T& val) {
  return a < val ? a = val, 1 : 0;
}
inline unsigned long long isqrt(unsigned long long k) {
  unsigned long long r = sqrt(k) + 1;
  while (r * r > k) r--;
  return r;
}
inline long long icbrt(long long k) {
  long long r = cbrt(k) + 1;
  while (r * r * r > k) r--;
  return r;
}
inline void addmod(int& a, int val, int p = MOD) {
  if ((a = (a + val)) >= p) a -= p;
}
inline void submod(int& a, int val, int p = MOD) {
  if ((a = (a - val)) < 0) a += p;
}
inline int mult(int a, int b, int p = MOD) { return (long long)a * b % p; }
inline int inv(int a, int p = MOD) { return fpow(a, p - 2, p); }
inline int sign(long double x) { return x < -EPS ? -1 : x > +EPS; }
inline int sign(long double x, long double y) { return sign(x - y); }
mt19937 mt(chrono::high_resolution_clock::now().time_since_epoch().count());
inline int myrand() { return abs((int)mt()); }
struct point_t {
  int x, y, ix, c;
  point_t(int x = 0, int y = 0, int ix = 0, int c = 0)
      : x(x), y(y), ix(ix), c(c) {}
  int operator<(const point_t& rhs) const {
    return make_pair(y, x) < make_pair(rhs.y, rhs.x);
  }
  int operator==(const point_t& rhs) const {
    return make_pair(y, x) == make_pair(rhs.y, rhs.x);
  }
  point_t operator-(const point_t& rhs) const {
    return point_t(x - rhs.x, y - rhs.y);
  }
};
long long cross(point_t a, point_t b) {
  return (long long)a.x * b.y - (long long)a.y * b.x;
}
long long area(point_t a, point_t b, point_t c) {
  return cross(a, b) + cross(b, c) + cross(c, a);
}
int inside(point_t a, point_t b, point_t c, point_t p) {
  return abs(area(a, b, c)) ==
         abs(area(p, a, b)) + abs(area(p, b, c)) + abs(area(p, c, a));
}
void ConvexHull(vector<point_t>& pts) {
  sort(pts.begin(), pts.end());
  pts.erase(unique(pts.begin(), pts.end()), pts.end());
  vector<point_t> up, dn;
  for (int i = 0; i < pts.size(); i++) {
    while (up.size() > 1 && area(up[up.size() - 2], up.back(), pts[i]) > 0)
      up.pop_back();
    while (dn.size() > 1 && area(dn[dn.size() - 2], dn.back(), pts[i]) < 0)
      dn.pop_back();
    up.push_back(pts[i]);
    dn.push_back(pts[i]);
  }
  pts = dn;
  for (int i = up.size() - 2; i >= 1; i--) pts.push_back(up[i]);
}
const int maxn = 1e3 + 5;
int n;
vector<point_t> p;
int used[maxn];
vector<pair<int, int> > res;
void solve(point_t a, point_t b, point_t c, vector<point_t> pts) {
  for (point_t p : {a, b, c}) used[p.ix] = 1;
  vector<point_t> npts;
  for (point_t p : pts) {
    if (inside(a, b, c, p) && !used[p.ix]) {
      npts.push_back(p);
    }
  }
  pts = npts;
  vector<point_t> g[2];
  for (point_t p : {a, b, c}) {
    g[p.c].push_back(p);
  }
  if (int((g[0]).size()) > int((g[1]).size())) {
    swap(g[0], g[1]);
  }
  if (int((g[0]).size())) {
    for (point_t p : pts) {
      if (p.c == g[0][0].c) {
        res.push_back(make_pair(p.ix, g[0][0].ix));
        solve(p, a, b, pts);
        solve(p, b, c, pts);
        solve(p, c, a, pts);
        return;
      }
    }
  }
  for (point_t p : pts) {
    for (point_t q : {a, b, c}) {
      if (p.c == q.c) {
        res.push_back(make_pair(p.ix, q.ix));
        break;
      }
    }
    solve(p, a, b, pts);
    solve(p, b, c, pts);
    solve(p, c, a, pts);
    return;
  }
}
void chemthan() {
  cin >> n;
  p.resize(n);
  vector<point_t> pts;
  for (int i = (0); i < (n); ++i) {
    cin >> p[i].x >> p[i].y >> p[i].c;
    p[i].ix = i;
    pts.push_back(p[i]);
  }
  ConvexHull(pts);
  for (point_t p : pts) used[p.ix] = 1;
  int st = 0;
  for (int i = (0); i < (int((pts).size())); ++i) {
    int j = (i + int((pts).size()) - 1) % int((pts).size());
    if (pts[i].c != pts[j].c) {
      st = i;
    }
  }
  vector<point_t> npts;
  for (int i = (0); i < (int((pts).size())); ++i) {
    int j = (i + st) % int((pts).size());
    npts.push_back(pts[j]);
  }
  pts = npts;
  int ed = 0;
  while (ed < int((pts).size()) && pts[ed].c == pts[0].c) ed++;
  for (int i = (ed); i < (int((pts).size())); ++i)
    if (pts[i].c == pts[0].c) {
      cout << "Impossible\n";
      return;
    }
  for (int i = (0); i < (ed - 1); ++i) {
    res.push_back(make_pair(pts[i].ix, pts[i + 1].ix));
  }
  for (int i = (ed); i < (int((pts).size()) - 1); ++i) {
    res.push_back(make_pair(pts[i].ix, pts[i + 1].ix));
  }
  if (ed == int((pts).size())) {
    int found = 0;
    for (point_t q : p) {
      if (q.c != pts[0].c) {
        for (int i = (0); i < (int((pts).size())); ++i) {
          int j = (i + 1) % int((pts).size());
          solve(q, pts[i], pts[j], p);
        }
        found = 1;
        break;
      }
    }
    if (!found) {
      for (int i = (1); i < (int((pts).size()) - 1); ++i) {
        solve(pts[0], pts[i], pts[i + 1], p);
      }
    }
    for (pair<int, int>& e : res) {
      if (e.first > e.second) {
        swap(e.first, e.second);
      }
    }
    sort((res).begin(), (res).end()),
        (res).erase(unique((res).begin(), (res).end()), (res).end());
    cout << int((res).size()) << "\n";
    for (pair<int, int> e : res) {
      cout << e.first << " " << e.second << "\n";
    }
    return;
  }
  for (int i = (0); i < (ed - 1); ++i) {
    solve(pts[ed], pts[i], pts[i + 1], p);
  }
  for (int i = (ed); i < (int((pts).size()) - 1); ++i) {
    solve(pts[0], pts[i], pts[i + 1], p);
  }
  for (pair<int, int>& e : res) {
    if (e.first > e.second) {
      swap(e.first, e.second);
    }
  }
  sort((res).begin(), (res).end()),
      (res).erase(unique((res).begin(), (res).end()), (res).end());
  cout << int((res).size()) << "\n";
  for (pair<int, int> e : res) {
    cout << e.first << " " << e.second << "\n";
  }
}
int main(int argc, char* argv[]) {
  ios_base::sync_with_stdio(0), cin.tie(0);
  if (argc > 1) {
    assert(freopen(argv[1], "r", stdin));
  }
  if (argc > 2) {
    assert(freopen(argv[2], "wb", stdout));
  }
  chemthan();
  cerr << "\nTime elapsed: " << 1000 * clock() / CLOCKS_PER_SEC << "ms\n";
  return 0;
}
