#include <bits/stdc++.h>
using namespace std;
template <typename T>
using vc = vector<T>;
using pii = pair<long long, long long>;
void xmax(long long& a, long long b) { a = max(a, b); }
void xmin(long long& a, long long b) { a = min(a, b); }
void print(vc<long long>& a, string second) {
  cerr << "prinitng " << second << "\n";
  for (long long i = 0; i < a.size(); i++) {
    cerr << a[i] << " ";
  }
  cerr << endl;
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  long long n, m, k;
  cin >> n >> m >> k;
  vc<long long> a(k);
  vc<long long> marked(n);
  for (long long i = 0; i < k; i++) {
    cin >> a[i];
    a[i]--;
    marked[a[i]] = 1;
  }
  long long geht = 1;
  if (k == n) geht = 0;
  if (m > n * (n - 1) / 2 - k + 1) geht = 0;
  if (!geht) {
    cout << "-1\n";
  } else {
    long long mitte;
    for (long long i = 0; i < n; i++) {
      if (marked[i] == 0) {
        mitte = i;
        break;
      }
    }
    long long l = a[0];
    long long r = a[1];
    vc<vc<long long> > no(n, vc<long long>(n));
    no[l][r] = 1;
    no[r][l] = 1;
    for (long long i = 0; i < n; i++) {
      no[i][i] = 1;
      no[mitte][i] = 1;
      no[i][mitte] = 1;
    }
    for (long long i = 0; i < k; i++) {
      no[a[i]][r] = 1;
      no[r][a[i]] = 1;
    }
    for (long long i = 0; i < n; i++) {
      if (i == mitte) continue;
      cout << i + 1 << " " << mitte + 1 << "\n";
    }
    long long anz = n - 1;
    for (long long i = 0; i < n && anz < m; i++) {
      for (long long j = i + 1; j < n && anz < m; j++) {
        if (no[i][j]) continue;
        cout << i + 1 << " " << j + 1 << "\n";
        anz++;
      }
    }
  }
}
