#include <bits/stdc++.h>
const int MAXN = 1010;
struct vec {
  int x, y, c, id;
  vec() { x = y = 0; }
  vec(int a, int b) { x = a, y = b; }
  vec operator+(vec b) const { return vec(x + b.x, y + b.y); }
  vec operator-(vec b) const { return vec(x - b.x, y - b.y); }
  int operator^(vec b) const { return x * b.y - y * b.x; }
  bool operator<(const vec& b) const { return x == b.x ? y < b.y : x < b.x; }
  friend std::ostream& operator<<(std::ostream& out, vec x) {
    out << '(' << x.x << ',' << x.y << ',' << x.c << ')';
    return out;
  }
  friend std::istream& operator>>(std::istream& in, vec& x) {
    in >> x.x >> x.y >> x.c;
    return in;
  }
};
int cross(vec a, vec b, vec c) { return (b - a) ^ (c - a); }
void polar(std::vector<vec>& li) {
  std::iter_swap(li.begin(), std::min_element(li.begin(), li.end()));
  vec spe = li[0];
  const auto cmp = [spe](vec a, vec b) { return cross(spe, a, b) > 0; };
  std::sort(li.begin() + 1, li.end(), cmp);
}
std::vector<vec> convex(std::vector<vec> li) {
  polar(li);
  static vec st[MAXN];
  int top = 0;
  for (auto t : li) {
    while (top > 1 && cross(st[top - 1], st[top], t) <= 0) --top;
    st[++top] = t;
  }
  return std::vector<vec>(st + 1, st + 1 + top);
}
std::vector<std::pair<int, int> > ansl;
inline int sgn(int x) { return x < 0 ? -1 : (x > 0); }
inline bool contain(vec A, vec B, vec C, vec O) {
  int x = sgn(cross(A, B, O));
  int y = sgn(cross(B, C, O));
  int z = sgn(cross(C, A, O));
  return x && y && z && x == y && y == z;
}
int n;
std::vector<vec> ps;
void solve(vec A, vec B, vec C) {
  for (int i = 1; i <= n; ++i)
    if (contain(A, B, C, ps[i]) && ps[i].c == A.c) {
      ansl.emplace_back(A.id, ps[i].id);
      solve(ps[i], B, C);
      solve(B, A, ps[i]);
      solve(C, A, ps[i]);
      return;
    }
  for (int i = 1; i <= n; ++i)
    if (contain(A, B, C, ps[i])) ansl.emplace_back(B.id, ps[i].id);
}
int main() {
  std::ios_base::sync_with_stdio(false), std::cin.tie(0);
  std::cin >> n;
  ps.resize(n);
  int c1 = 0;
  for (int i = 0; i < n; ++i) std::cin >> ps[i], ps[i].id = i, c1 += ps[i].c;
  if (c1 == n || !c1) {
    for (int i = 1; i < n; ++i) ansl.emplace_back(1, i + 1);
  }
  std::vector<vec> cx = convex(ps);
  const int S = cx.size();
  auto pr = [S](int x) {
    x -= 1;
    return x + (x >> 31 & S);
  };
  auto nt = [S](int x) {
    x += 1 - S;
    return x + (x >> 31 & S);
  };
  int l = -1, r = -1;
  for (int i = 0; i < S; ++i)
    if (cx[i].c != cx[0].c) {
      r = l = i;
      int ct = 0;
      while (cx[r].c == cx[l].c) r = nt(r), ++ct;
      for (auto t : cx) ct -= t.c != cx[0].c;
      if (ct) {
        std::cout << "Impossible" << std::endl;
        return 0;
      }
      break;
    }
  if (l == -1) {
    for (int i = 0; i + 1 < S; ++i) ansl.emplace_back(cx[i].id, cx[i + 1].id);
    for (int i = 0; i < n; ++i)
      if (ps[i].c != cx[0].c) {
        for (int j = 0; j < S; ++j) solve(ps[i], cx[j], cx[nt(r)]);
        break;
      }
  } else {
    auto solve = [pr, nt, cx](int l, int r) {
      int now = l, tar = pr(l);
      while (nt(now) != r) {
        int t = nt(now);
        ansl.emplace_back(cx[now].id, cx[t].id);
        ::solve(cx[tar], cx[now], cx[t]);
        now = t;
      }
    };
    solve(l, r), solve(r, l);
  }
  std::cout << ansl.size() << std::endl;
  for (auto t : ansl) std::cout << t.first << ' ' << t.second << '\n';
  return 0;
}
