#include <bits/stdc++.h>
using namespace std;
inline int read() {
  int f = 1, x = 0;
  char ch = getchar();
  while (!isdigit(ch)) {
    if (ch == '-') f = -1;
    ch = getchar();
  }
  while (isdigit(ch)) {
    x = x * 10 + ch - '0';
    ch = getchar();
  }
  return x * f;
}
int n;
pair<int, int> a[1005], b[1005];
vector<pair<int, int> > ans;
void oper(int x, int y) {
  for (int i = 1; i <= n - 3; ++i) {
    if (a[i].first == x && a[i].second == y) {
      ans.push_back(make_pair(x, y));
      a[i].first = 1;
      for (int j = 1; j <= n - 3; ++j) {
        if (a[j].first == x || a[j].second == x) {
          int t = a[j].first == x ? a[j].second : a[j].first;
          if (t < x || t > y) continue;
          for (int k = 1; k <= n - 3; ++k) {
            if (a[k].first == y || a[k].second == y) {
              int tt = a[k].first == y ? a[k].second : a[k].first;
              if (tt < x || tt > y) continue;
              if (t == tt) {
                a[i].second = t;
                return;
              }
            }
          }
        }
      }
      int t = x + 1;
      for (int k = 1; k <= n - 3; ++k) {
        if (a[k].first == y || a[k].second == y) {
          int tt = a[k].first == y ? a[k].second : a[k].first;
          if (tt < x || tt > y) continue;
          if (t == tt) {
            a[i].second = t;
            return;
          }
        }
      }
      t = y - 1;
      for (int j = 1; j <= n - 3; ++j) {
        if (a[j].first == x || a[j].second == x) {
          int tt = a[j].first == x ? a[j].second : a[j].first;
          if (tt < x || tt > y) continue;
          if (t == tt) {
            a[i].second = t;
            return;
          }
        }
      }
      a[i].second = y - 1;
      return;
    }
  }
}
void inv_oper(int x, int y) {
  for (int i = 1; i <= n - 3; ++i) {
    if (b[i].first == x && b[i].second == y) {
      b[i].first = 1;
      for (int j = 1; j <= n - 3; ++j) {
        if (b[j].first == x || b[j].second == x) {
          int t = b[j].first == x ? b[j].second : b[j].first;
          if (t < x || t > y) continue;
          for (int k = 1; k <= n - 3; ++k) {
            if (b[k].first == y || b[k].second == y) {
              int tt = b[k].first == y ? b[k].second : b[k].first;
              if (tt < x || tt > y) continue;
              if (t == tt) {
                b[i].second = t;
                ans.push_back(b[i]);
                return;
              }
            }
          }
        }
      }
      int t = x + 1;
      for (int k = 1; k <= n - 3; ++k) {
        if (b[k].first == y || b[k].second == y) {
          int tt = b[k].first == y ? b[k].second : b[k].first;
          if (tt < x || tt > y) continue;
          if (t == tt) {
            b[i].second = t;
            ans.push_back(b[i]);
            return;
          }
        }
      }
      t = y - 1;
      for (int j = 1; j <= n - 3; ++j) {
        if (b[j].first == x || b[j].second == x) {
          int tt = b[j].first == x ? b[j].second : b[j].first;
          if (tt < x || tt > y) continue;
          if (t == tt) {
            b[i].second = t;
            ans.push_back(b[i]);
            return;
          }
        }
      }
      b[i].second = y - 1;
      ans.push_back(b[i]);
      return;
    }
  }
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  n = read();
  for (int i = 1; i <= n - 3; ++i) {
    int x = read(), y = read();
    if (x > y) swap(x, y);
    a[i] = make_pair(x, y);
  }
  for (int i = 1; i <= n - 3; ++i) {
    int x = read(), y = read();
    if (x > y) swap(x, y);
    b[i] = make_pair(x, y);
  }
  vector<int> vc1;
  while (true) {
    vc1.clear();
    vc1.push_back(2);
    vc1.push_back(n);
    for (int i = 1; i <= n - 3; ++i) {
      if (a[i].first == 1) vc1.push_back(a[i].second);
    }
    if (vc1.size() == n - 1) break;
    sort(vc1.begin(), vc1.end());
    for (int i = 0; i + 1 < (int)vc1.size(); ++i) {
      if (vc1[i + 1] - vc1[i] > 1) {
        oper(vc1[i], vc1[i + 1]);
      }
    }
  }
  int tp = ans.size();
  while (true) {
    vc1.clear();
    vc1.push_back(2);
    vc1.push_back(n);
    for (int i = 1; i <= n - 3; ++i) {
      if (b[i].first == 1) vc1.push_back(b[i].second);
    }
    if (vc1.size() == n - 1) break;
    sort(vc1.begin(), vc1.end());
    for (int i = 0; i + 1 < (int)vc1.size(); ++i) {
      if (vc1[i + 1] - vc1[i] > 1) {
        inv_oper(vc1[i], vc1[i + 1]);
      }
    }
  }
  cout << ans.size() << endl;
  for (int i = 0; i < tp; ++i)
    cout << ans[i].first << " " << ans[i].second << endl;
  for (int i = ans.size() - 1; i >= tp; --i)
    cout << ans[i].first << " " << ans[i].second << endl;
  return 0;
}
