#include <bits/stdc++.h>
using namespace std;
typedef struct {
  int u, v;
} E;
const int maxn = 300 + 50;
int n, m, k;
int ne, nv;
int v[maxn];
E edge[maxn * maxn];
bool has[maxn][maxn];
bool mark[maxn];
bool choose[maxn];
int mv[maxn];
void add_v(int i) {
  mv[nv] = i;
  choose[i] = 1;
  nv++;
}
void add_e(int u, int v) {
  if (u > v) swap(u, v);
  if (has[u][v]) return;
  if (!choose[u]) add_v(u);
  if (!choose[v]) add_v(v);
  has[u][v] = 1;
  edge[ne].u = u;
  edge[ne].v = v;
  ne++;
}
void solve() {
  bool ok = 1;
  for (int i = 1; i <= n; i++) has[i][i] = 1;
  if (n == k) {
    ok = 0;
  }
  nv = 0, ne = 0;
  for (int i = 0; i <= 1; i++) {
    add_v(v[i]);
  }
  for (int i = 1; i <= n; i++) {
    if (!choose[i] && !mark[i]) {
      add_e(mv[0], i);
      add_e(mv[1], i);
      break;
    }
  }
  for (int i = 1; i <= n; i++) {
    if (!mark[i])
      for (int j = 1; j <= n; j++) {
        add_e(i, j);
      }
  }
  for (int i = 2; i < k; i++) {
    add_e(v[0], v[i]);
  }
  for (int i = 2; i < k; i++) {
    for (int j = 2; j < k; j++) {
      add_e(v[i], v[j]);
    }
  }
  if (!ok) {
    cout << -1 << endl;
    return;
  }
  if (ne >= m) {
    for (int i = 0; i < m; i++) {
      cout << edge[i].u << " " << edge[i].v << endl;
    }
  } else
    cout << -1 << endl;
}
int main() {
  cin >> n >> m >> k;
  for (int i = 0; i < k; i++) {
    cin >> v[i];
    mark[v[i]] = 1;
  }
  solve();
  return 0;
}
