#include <bits/stdc++.h>
using namespace std;
void solve() {
  long long n, m, k;
  cin >> n >> m >> k;
  vector<int> a(k);
  vector<int> ispresent(n, false);
  for (int i = 0; i < k; i++) {
    cin >> a[i];
    a[i]--;
    ispresent[a[i]] = true;
  }
  if (k == n) {
    cout << "-1" << endl;
  } else if (m > n * (n - 1) / 2 - k + 1) {
    cout << "-1" << endl;
  } else {
    int cannot_be_deleted;
    for (int i = 0; i < n; i++) {
      if (!ispresent[i]) {
        cannot_be_deleted = i;
        break;
      }
    }
    int fixed = a[0];
    vector<vector<bool> > edges(n);
    for (int i = 0; i < n; i++) {
      edges[i].resize(n);
      for (int j = 0; j < n; j++) {
        if (i != j) {
          edges[i][j] = true;
        } else {
          edges[i][j] = false;
        }
      }
    }
    for (int i = 1; i < k; i++) {
      edges[fixed][a[i]] = false;
      edges[a[i]][fixed] = false;
    }
    long long extra = n * (n - 1) / 2 - k + 1 - m;
    bool done = false;
    if (extra == 0) {
      done = true;
    }
    while (!done) {
      for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
          if (edges[i][j] && i != cannot_be_deleted && j != cannot_be_deleted) {
            edges[i][j] = false;
            edges[j][i] = false;
            extra--;
            if (extra == 0) {
              done = true;
              break;
            }
          }
        }
        if (done) {
          break;
        }
      }
    }
    for (int i = 0; i < n; i++) {
      for (int j = i + 1; j < n; j++) {
        if (edges[i][j]) {
          cout << i + 1 << " " << j + 1 << endl;
        }
      }
    }
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int t = 1;
  while (t--) {
    solve();
  }
  return 0;
}
