#include <bits/stdc++.h>
using namespace std;
const int M = 1e3 + 5;
int n, tot1 = 0, tot2 = 0;
bool vis[M][M];
struct CuCun {
  int x, y;
} A[M], B[M];
int read() {
  int x = 0, y = 1;
  char ch = getchar();
  while (ch < '0' || ch > '9') {
    if (ch == '-') y = -1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9') {
    x = x * 10 + ch - '0';
    ch = getchar();
  }
  return x * y;
}
void filp(int a, int b, bool inv) {
  int x = -1, y;
  for (int i = 1; i <= n; i++) {
    if (vis[a][i] && vis[b][i]) {
      if (x == -1)
        x = i;
      else {
        y = i;
        break;
      }
    }
  }
  vis[a][b] = vis[b][a] = 0;
  vis[x][y] = vis[y][x] = 1;
  if (inv)
    B[++tot2].x = x, B[tot2].y = y;
  else
    A[++tot1].x = a, A[tot1].y = b;
}
void solve(bool inv) {
  memset(vis, 0, sizeof(vis));
  for (int i = 1; i <= n; i++) vis[i][i % n + 1] = vis[i % n + 1][i] = 1;
  for (int i = 1; i <= n - 3; i++) {
    int a = read(), b = read();
    vis[a][b] = vis[b][a] = 1;
  }
  for (int i = 2; i <= n;) {
    if (vis[1][i])
      i++;
    else {
      int j;
      for (j = i + 1; !vis[1][j]; j++)
        ;
      filp(i - 1, j, inv);
    }
  }
}
int main() {
  n = read();
  solve(0), solve(1);
  printf("%d\n", tot1 + tot2);
  for (int i = 1; i <= tot1; i++) printf("%d %d\n", A[i].x, A[i].y);
  for (int i = tot2; i >= 1; i--) printf("%d %d\n", B[i].x, B[i].y);
}
