#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, m, k, i, j;
  int a[300] = {0};
  int b[300][300] = {0};
  vector<int> v, w;
  scanf("%d %d %d", &n, &m, &k);
  for (i = 0; i < k; i++) {
    int x;
    scanf("%d", &x);
    x--;
    a[x] = 1;
    v.push_back(x);
  }
  for (i = 0; i < n; i++) {
    if (a[i] == 0) w.push_back(i);
  }
  while (v.size() < 2) {
    v.push_back(w.back());
    w.pop_back();
  }
  if (w.size() == 0) {
    puts("-1");
    return 0;
  }
  sort(v.begin(), v.end());
  sort(w.begin(), w.end());
  if ((v.size() - 1) * (v.size() - 2) / 2 + w.size() * (w.size() - 1) / 2 +
          v.size() * w.size() <
      m) {
    puts("-1");
    return 0;
  }
  a[v[0]] = 2;
  for (i = 1; i < v.size(); i++) a[v[i]] = 1;
  for (i = 0; i < w.size(); i++) a[w[i]] = 0;
  for (i = 1; i < v.size() - 1; i++) b[v[i]][v[i + 1]] = b[v[i + 1]][v[i]] = 1;
  for (i = 0; i < w.size() - 1; i++) b[w[i]][w[i + 1]] = b[w[i + 1]][w[i]] = 1;
  b[v[0]][w[0]] = b[w[0]][v[0]] = 1;
  b[v[1]][w[0]] = b[w[0]][v[1]] = 1;
  m -= n - 1;
  for (i = 0; i < n; i++) {
    for (j = i + 1; j < n; j++) {
      if (a[i] + a[j] == 3) continue;
      if (b[i][j] == 1) continue;
      if (m == 0) break;
      b[i][j] = 1;
      m--;
    }
  }
  for (i = 0; i < n; i++) {
    for (j = i + 1; j < n; j++) {
      if (b[i][j] == 1) printf("%d %d\n", i + 1, j + 1);
    }
  }
  return 0;
}
