#include <bits/stdc++.h>
using namespace std;
int n, m, k;
int arr[310];
int adj[310][310];
int cnt[310];
int h;
int ans = 0;
int main(void) {
  scanf("%d%d%d", &n, &m, &k);
  for (int i = 1; i <= k; i++) scanf("%d", arr + i), cnt[arr[i]]++;
  sort(arr + 1, arr + 1 + k);
  if (k == n) {
    printf("-1");
    return 0;
  }
  if (m > n * (n - 1) / 2 - k + 1) {
    printf("-1");
    return 0;
  }
  for (int i = 1; i <= n; i++)
    if (cnt[i] == 0) h = i;
  for (int i = 1; i <= n; i++) {
    for (int j = i + 1; j <= n; j++) {
      adj[i][j] = 1;
    }
  }
  for (int i = 2; i <= k; i++) adj[arr[1]][arr[i]] = 0;
  for (int i = 1; i <= n; i++)
    if (i != h) printf("%d %d\n", min(i, h), max(i, h));
  ans = n - 1;
  if (ans == m) return 0;
  for (int i = 1; i <= n; i++) {
    for (int j = i + 1; j <= n; j++) {
      if (adj[i][j] == 0) continue;
      if (i == h || j == h) continue;
      printf("%d %d\n", i, j);
      if (++ans == m) return 0;
    }
  }
  return 0;
}
