#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 10;
int n, m, a[N], b[N], D, A;
int Pow(int x, int y, int M) {
  int res = 1;
  while (y) {
    if (y % 2 == 1) res = 1ll * res * x % M;
    x = 1ll * x * x % M;
    y /= 2;
  }
  return res;
}
int nv(int x) { return Pow(x, m - 2, m); }
int main() {
  int s1, s2;
  s1 = s2 = 0;
  scanf("%d%d", &m, &n);
  for (int i = 1; i <= n; i++) {
    scanf("%d", &a[i]);
    s1 = (s1 + a[i]) % m;
    s2 = (s2 + 1ll * a[i] * a[i]) % m;
  }
  if (n == 1) {
    printf("%d 0", a[1]);
    return 0;
  }
  if (m == n) {
    puts("0 1");
    return 0;
  }
  sort(a + 1, a + 1 + n);
  for (int i = 2; i <= n; i++) {
    D = (a[i] - a[1] + m) % m;
    A = 1ll * (s1 - 1ll * n * (n - 1) / 2 % m * D % m + m) * nv(n) % m;
    int t = (1ll * n * A % m * A % m + 1ll * n * (n - 1) % m * D % m * A % m +
             1ll * n * (2 * n - 1) * (n - 1) / 6 % m * D % m * D % m) %
            m;
    if (t == s2) {
      b[1] = A;
      for (int i = 2; i <= n; i++) b[i] = (b[i - 1] + D) % m;
      sort(b + 1, b + n + 1);
      int flag = 1;
      for (int i = 1; i <= n; i++) flag &= (b[i] == a[i]);
      if (flag) {
        printf("%d %d\n", A, D);
        return 0;
      }
    }
  }
  puts("-1");
  return 0;
}
