#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;
}
int a[110101];
map<int, int> mp;
int main() {
  int m, n;
  gn(m, n);
  for (int i = 0; i < n; i++) {
    gn(a[i]);
    mp[a[i]] = 1;
  }
  if (n == 1 || n == m) {
    printf("%d 1\n", a[0]);
    return 0;
  }
  int judge = 0;
  if (m < 2 * n) {
    n = 0;
    judge = 1;
    for (int i = 0; i < m; i++)
      if (!mp.count(i)) {
        a[n++] = i;
      }
    mp.clear();
    for (int i = 0; i < n; i++) mp[a[i]] = 1;
  }
  if (n == 1) {
    printf("%d 1\n", (a[0] + 1) % m);
    return 0;
  }
  int D = (long long)(a[1] - a[0] + m) % m;
  int cnt = 0;
  for (int i = 0; i < n; i++) {
    if (!mp.count((a[i] + D) % m)) cnt++;
  }
  int d = (long long)D * power(cnt, m - 2, m) % m;
  cnt = 0;
  long long tmp;
  for (int i = 0; i < n; i++) {
    if (!mp.count((a[i] - d + m) % m)) cnt++, tmp = a[i];
  }
  if (cnt != 1) {
    puts("-1");
    return 0;
  }
  if (judge) tmp = (tmp + (long long)n * d) % m;
  printsp(tmp);
  printsp(d);
  return 0;
}
