#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e5 + 10;
int a[maxn];
set<int> S;
long long qpow(long long a, long long b, long long mod) {
  long long ret = 1LL;
  while (b) {
    if (b & 1) ret = ret * a % mod;
    a = a * a % mod;
    b >>= 1;
  }
  return ret;
}
long long inv(long long x, long long mod) { return qpow(x, mod - 2, mod); }
int main(void) {
  int n, m;
  scanf("%d %d", &m, &n);
  if (n + n < m) {
    for (int i = 1; i <= n; i++) scanf("%d", a + i), S.insert(a[i]);
    if (n == 1) {
      printf("%d 0\n", a[1]);
      return 0;
    }
    int kd = (a[2] - a[1] + m) % m;
    int cnt = 0;
    for (int i = 1; i <= n; i++) {
      int nxt = (a[i] + kd) % m;
      if (S.find(nxt) != S.end()) cnt++;
    }
    int k = n - cnt;
    if (!k) {
      printf("%d %d\n", a[1], kd);
      return 0;
    }
    int d = (long long)kd * inv(k, m) % m;
    cnt = 0;
    for (int i = 0; i < n; i++)
      if (S.find((a[1] - (long long)i * d % m + m) % m) != S.end()) cnt++;
    if (cnt == n) {
      printf("%I64d %d\n", (a[1] - (long long)(n - 1) * d % m + m) % m, d);
      return 0;
    }
    for (int i = 1; i < n; i++) {
      if (S.find((a[1] + (long long)(i - n) * d % m + m) % m) != S.end()) cnt--;
      if (S.find((a[1] + (long long)i * d % m + m) % m) != S.end()) cnt++;
      if (cnt == n) {
        printf("%I64d %d\n", (a[1] + (long long)(i - n + 1) * d % m + m) % m,
               d);
        return 0;
      }
    }
    puts("-1");
  } else {
    for (int i = 0; i < m; i++) S.insert(i);
    for (int i = 1; i <= n; i++) scanf("%d", a + i), S.erase(a[i]);
    n = m - n;
    set<int>::iterator it = S.begin();
    for (int i = 1; i <= n; i++) a[i] = *(it++);
    if (n == 0) {
      printf("0 1\n");
      return 0;
    }
    if (n == 1) {
      printf("%d 1\n", (a[1] + n) % m);
      return 0;
    }
    int kd = (a[2] - a[1] + m) % m;
    int cnt = 0;
    for (int i = 1; i <= n; i++) {
      int nxt = (a[i] + kd) % m;
      if (S.find(nxt) != S.end()) cnt++;
    }
    int k = n - cnt;
    if (!k) {
      printf("%d %d\n", (a[1] + (long long)n * kd) % m, kd);
      return 0;
    }
    int d = (long long)kd * inv(k, m) % m;
    cnt = 0;
    for (int i = 0; i < n; i++)
      if (S.find((a[1] - (long long)i * d % m + m) % m) != S.end()) cnt++;
    if (cnt == n) {
      printf("%I64d %d\n",
             (a[1] - (long long)(n - 1) * d % m + m + (long long)n * d) % m, d);
      return 0;
    }
    for (int i = 1; i < n; i++) {
      if (S.find((a[1] + (long long)(i - n) * d % m + m) % m) != S.end()) cnt--;
      if (S.find((a[1] + (long long)i * d % m + m) % m) != S.end()) cnt++;
      if (cnt == n) {
        printf(
            "%I64d %d\n",
            (a[1] + (long long)(i - n + 1) * d % m + m + (long long)n * d) % m,
            d);
        return 0;
      }
    }
    puts("-1");
  }
  return 0;
}
