#include <bits/stdc++.h>
using namespace std;
template <typename T, typename U>
inline void smin(T &a, U b) {
  if (a > b) a = b;
}
template <typename T, typename U>
inline void smax(T &a, U b) {
  if (a < b) a = b;
}
template <typename T>
inline void gn(T &first) {
  char c, sg = 0;
  while (c = getchar(), (c > '9' || c < '0') && c != '-')
    ;
  for ((c == '-' ? sg = 1, c = getchar() : 0), first = 0; c >= '0' && c <= '9';
       c = getchar())
    first = (first << 1) + (first << 3) + c - '0';
  if (sg) first = -first;
}
template <class T, class T1>
inline void gn(T &first, T1 &second) {
  gn(first);
  gn(second);
}
template <class T, class T1, class T2>
inline void gn(T &first, T1 &second, T2 &z) {
  gn(first);
  gn(second);
  gn(z);
}
template <typename T>
inline void print(T first) {
  if (first < 0) {
    putchar('-');
    return print(-first);
  }
  if (first < 10) {
    putchar('0' + first);
    return;
  }
  print(first / 10);
  putchar(first % 10 + '0');
}
template <typename T>
inline void println(T first) {
  print(first), putchar('\n');
}
template <typename T>
inline void printsp(T first) {
  print(first), putchar(' ');
}
int power(int a, int b, int m, int ans = 1) {
  for (; b; b >>= 1, a = 1LL * a * a % m)
    if (b & 1) ans = 1LL * ans * a % m;
  return ans;
}
map<int, bool> mp;
int main() {
  const int N = 100100;
  static int nn, A[N], a[N], flag[N << 1];
  int p, n;
  gn(p, n);
  nn = n;
  for (int i = 0; i < n; i++) gn(A[i]);
  sort(A, A + n);
  if (n == 1) {
    printf("%d %d\n", A[0], 0);
    return 0;
  }
  if (n == 2) {
    printf("%d %d\n", A[0], A[1] - A[0]);
    return 0;
  }
  if (n == p) {
    puts("0 1");
    return 0;
  }
  if (n > p / 2) {
    for (int i = 0; i < n; i++) flag[A[i]] = 1;
    n = 0;
    for (int i = 0; i < p; i++)
      if (!flag[i]) a[n++] = i;
  } else
    for (int i = 0; i < n; i++) a[i] = A[i];
  if (n == 1) {
    printf("%d %d\n", (a[0] + 1) % p, 1);
    return 0;
  }
  int d = a[1] - a[0], k = 0;
  for (int i = 0; i < n; i++) {
    int t = (a[i] + d) % p;
    mp[t] = true;
  }
  for (int i = 0; i < n; i++) {
    if (!mp.count(a[i])) k++;
  }
  d = (long long)d * power(k, p - 2, p) % p;
  mp.clear();
  for (int i = 0; i < nn; i++) mp[A[i]] = true;
  int cnt_st = 0, cnt_ed = 0, st;
  for (int i = 0; i < nn; i++) {
    int c1 = mp.count((A[i] + d) % p);
    int c2 = mp.count(((A[i] - d) % p + p) % p);
    if (!c1 && !c2) {
      puts("-1");
      return 0;
    }
    if (c1 && c2) continue;
    if (!c1) cnt_ed++;
    if (!c2) cnt_st++, st = A[i];
  }
  if (cnt_st == 1 && cnt_ed == 1) {
    printf("%d %d\n", st, d);
    return 0;
  }
  puts("-1");
  return 0;
}
