#include <bits/stdc++.h>
using namespace std;
const int MAXN = 305;
int n, m, k, x;
bool special[MAXN];
int parent[MAXN];
bool used[MAXN * MAXN];
vector<pair<int, int> > answer, edges;
int Find(int x) {
  if (parent[x] == x) return x;
  parent[x] = Find(parent[x]);
  return parent[x];
}
void Union(int u, int v) {
  u = Find(u);
  v = Find(v);
  if (u == v) return;
  parent[v] = u;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(NULL);
  int X = -1, Y = -1;
  cin >> n >> m >> k;
  for (int i = 0; i < k; i++) {
    cin >> x;
    special[x] = true;
  }
  for (int i = 1; i <= n; i++) {
    parent[i] = i;
  }
  for (int i = n; i >= 1; i--) {
    if (special[i] == false) continue;
    if (X == -1)
      X = i;
    else if (Y == -1)
      Y = i;
  }
  for (int i = 1; i <= n; i++) {
    for (int j = i + 1; j <= n; j++) {
      if ((i == X || j == X) && (special[i] == true && special[j] == true))
        continue;
      edges.push_back({i, j});
    }
  }
  if (edges.size() < m) {
    cout << "-1" << '\n';
    return 0;
  }
  for (int i = 0; i < edges.size(); i++) {
    if (answer.size() >= m) break;
    if (Find(edges[i].first) != Find(edges[i].second)) {
      used[i] = true;
      Union(edges[i].first, edges[i].second);
      answer.push_back(edges[i]);
    }
  }
  for (int i = 0; i < edges.size(); i++) {
    if (used[i] == false && answer.size() < m) {
      answer.push_back(edges[i]);
    }
  }
  for (int i = 2; i <= n; i++) {
    if (Find(1) != Find(i)) {
      cout << "-1" << '\n';
      return 0;
    }
  }
  for (int i = 0; i < m; i++) {
    cout << answer[i].first << " " << answer[i].second << '\n';
  }
}
