#include <bits/stdc++.h>
using namespace std;
const int inf = 0x3fffffff;
const long long mod = 1000000007;
const int maxn = 1e5 + 10;
long long ans1, ans2;
long long a[maxn], b[maxn];
long long fp(int n, long long k, long long m) {
  long long ans = 1, t = n;
  while (k) {
    if (k & 1) ans = (ans * t) % m;
    t = (t * t) % m;
    k /= 2;
  }
  return ans % m;
}
int main() {
  int n;
  long long m;
  scanf("%I64d%d", &m, &n);
  ans1 = ans2 = 0;
  for (int i = 1; i < n + 1; i++) {
    scanf("%I64d", &a[i]);
    a[i] %= m;
    ans1 = (ans1 + a[i]) % m;
    ans2 = (ans2 + a[i] * a[i] % m) % m;
  }
  if (n == 1) {
    printf("%I64d 0\n", a[1]);
    return 0;
  }
  sort(a + 1, a + n + 1);
  for (int i = 2; i < n + 1; i++) {
    long long d = (a[i] - a[1]) % m;
    long long x = (ans1 - 1ll * n * (n - 1) / 2 % m * d % m + m) % m *
                  fp(n, m - 2, m) % m;
    long long res = (n * x % m * x % m +
                     1ll * n * (n - 1) * (2 * n - 1) / 6 % m * d % m * d % m +
                     1ll * n * (n - 1) % m * d % m * x % m) %
                    m;
    if (res == ans2) {
      b[1] = x;
      for (int j = 2; j < n + 1; j++) {
        b[j] = (b[j - 1] + d) % m;
      }
      sort(b + 1, b + n + 1);
      bool f = true;
      for (int j = 1; j < n + 1; j++) {
        if (a[j] != b[j]) {
          f = false;
          break;
        }
      }
      if (f) {
        printf("%I64d %I64d\n", x, d);
        return 0;
      }
    }
  }
  puts("-1");
  return 0;
}
