#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:102400000,102400000")
using namespace std;
template <class T, class U>
inline void Max(T &a, U b) {
  if (a < b) a = b;
}
template <class T, class U>
inline void Min(T &a, U b) {
  if (a > b) a = b;
}
inline void add(int &a, int b) {
  a += b;
  while (a >= 1000000007) a -= 1000000007;
}
int pow(int a, int b) {
  int ans = 1;
  while (b) {
    if (b & 1) ans = ans * (long long)a % 1000000007;
    a = (long long)a * a % 1000000007;
    b >>= 1;
  }
  return ans;
}
int pow(int a, int b, int c) {
  long long ans = 1;
  while (b) {
    if (b & 1) ans = ans * a % c;
    a = 1LL * a * a % c;
    b >>= 1;
  }
  return ans;
}
int a[100010], b[100010];
int main() {
  int j, k, i, T, ca = 0, n, m, K;
  scanf("%d%d", &m, &n);
  long long s0 = 0, s1 = 0;
  for (int i = 0; i < n; i++) {
    scanf("%d", &a[i]);
    s0 = (s0 + a[i]) % m;
    s1 = (s1 + 1LL * a[i] * a[i]) % m;
  }
  sort(a, a + n);
  if (n == 1) {
    printf("%d 0\n", a[0]);
    return 0;
  } else if (n == m) {
    printf("%d 1\n", a[0]);
    return 0;
  } else {
    long long nnn = 1LL * n * (n - 1) * (2 * n - 1) / 6 % m;
    long long nn = 1LL * n * (n - 1) / 2;
    long long inv = pow(n, m - 2, m);
    for (int i = 1; i < n; i++) {
      int d = (a[i] - a[0]) % m;
      int first = (s0 - nn * d % m + m) * inv % m;
      long long tmp = 1LL * first * first % m * n % m;
      tmp += nnn * d % m * d % m;
      tmp += nn * 2 * d % m * first % m;
      if (tmp % m == s1) {
        b[0] = first;
        for (int j = 1; j < n; j++) b[j] = (b[j - 1] + d) % m;
        sort(b, b + n);
        bool ok = 1;
        for (int j = 0; j < n; j++)
          if (b[j] != a[j]) {
            ok = 0;
            break;
          }
        if (ok) {
          printf("%d %d\n", first, d);
          return 0;
        }
      }
    }
  }
  puts("-1");
  return 0;
}
