#include <bits/stdc++.h>
using namespace std;
const int MOD = (int)1e9 + 7;
const int INF = (int)1e9;
const long long LINF = (long long)1e18;
const long double PI = acos((long double)-1);
const long double EPS = 1e-9;
inline long long gcd(long long a, long long b) {
  long long r;
  while (b) {
    r = a % b;
    a = b;
    b = r;
  }
  return a;
}
inline long long lcm(long long a, long long b) { return a / gcd(a, b) * b; }
inline long long fpow(long long n, long long k, int p = MOD) {
  long long r = 1;
  for (; k; k >>= 1) {
    if (k & 1) r = r * n % p;
    n = n * n % p;
  }
  return r;
}
template <class T>
inline int chkmin(T& a, const T& val) {
  return val < a ? a = val, 1 : 0;
}
template <class T>
inline int chkmax(T& a, const T& val) {
  return a < val ? a = val, 1 : 0;
}
template <class T>
inline T isqrt(T k) {
  T r = sqrt(k) + 1;
  while (r * r > k) r--;
  return r;
}
template <class T>
inline T icbrt(T k) {
  T r = cbrt(k) + 1;
  while (r * r * r > k) r--;
  return r;
}
inline void addmod(int& a, int val, int p = MOD) {
  if ((a = (a + val)) >= p) a -= p;
}
inline void submod(int& a, int val, int p = MOD) {
  if ((a = (a - val)) < 0) a += p;
}
inline int mult(int a, int b, int p = MOD) { return (long long)a * b % p; }
inline int inv(int a, int p = MOD) { return fpow(a, p - 2, p); }
inline int sign(long double x) { return x < -EPS ? -1 : x > +EPS; }
inline int sign(long double x, long double y) { return sign(x - y); }
int p = (int)1e9 + 7;
template <class T, class mul, class dvd>
struct FiniteField {
  T x;
  template <class G>
  T normalize(G x) {
    if (x >= 0 && x < p) return x;
    x %= p;
    if (x < 0)
      x += p;
    else if (x >= p)
      x -= p;
    return x;
  }
  FiniteField() : x(0) {}
  template <class G>
  FiniteField(const G& y) {
    x = normalize(y);
  }
  FiniteField(const FiniteField& rhs) : x(rhs.x) {}
  template <class G>
  FiniteField operator()(const G& y) {
    x = normalize(y);
    return *this;
  }
  template <class G>
  FiniteField operator=(const G& y) {
    x = normalize(y);
    return *this;
  }
  int operator==(const FiniteField& rhs) const { return x == rhs.x; }
  int operator!=(const FiniteField& rhs) const { return x != rhs.x; }
  int operator<(const FiniteField& rhs) const { return x < rhs.x; }
  FiniteField operator++(int) {
    FiniteField res = *this;
    if ((++x) >= p) x -= p;
    return res;
  }
  FiniteField operator++() {
    if ((++x) >= p) x -= p;
    return *this;
  }
  FiniteField operator--(int) {
    FiniteField res = *this;
    if ((--x) < 0) x += p;
    return res;
  }
  FiniteField operator--() {
    if ((--x) < 0) x += p;
    return *this;
  }
  template <class G>
  FiniteField operator+=(const G& y) {
    if ((x += normalize(y)) >= p) x -= p;
    return *this;
  }
  template <class G>
  FiniteField operator-=(const G& y) {
    if ((x -= normalize(y)) < 0) x += p;
    return *this;
  }
  FiniteField operator+=(const FiniteField& rhs) {
    if ((x += rhs.x) >= p) x -= p;
    return *this;
  }
  FiniteField operator-=(const FiniteField& rhs) {
    if ((x -= rhs.x) < 0) x += p;
    return *this;
  }
  FiniteField operator+(const FiniteField& rhs) const {
    FiniteField res;
    res.x = x + rhs.x;
    if (res.x >= p) res.x -= p;
    return res;
  }
  FiniteField operator-(const FiniteField& rhs) const {
    FiniteField res;
    res.x = x - rhs.x;
    if (res.x < 0) res.x += p;
    return res;
  }
  template <class G>
  FiniteField operator*=(const G& y) {
    x = mul()(x, normalize(y), p);
    return *this;
  }
  template <class G>
  FiniteField operator/=(const G& y) {
    x = dvd()(x, normalize(y), p);
    return *this;
  }
  template <class G>
  FiniteField operator*(const G& y) const {
    FiniteField res;
    res.x = mul()(x, res.normalize(y), p);
    return res;
  }
  template <class G>
  FiniteField operator/(const G& y) const {
    FiniteField res;
    res.x = dvd()(x, res.normalize(y), p);
    return res;
  }
  FiniteField operator*(const FiniteField& rhs) const {
    FiniteField res;
    res.x = mul()(x, rhs.x, p);
    return res;
  }
  FiniteField operator/(const FiniteField& rhs) const {
    FiniteField res;
    res.x = dvd()(x, rhs.x, p);
    return res;
  }
  template <class G>
  friend FiniteField operator*(const G& y, const FiniteField& rhs) {
    FiniteField res;
    res.x = res.normalize(y);
    return res * rhs;
  }
  template <class G>
  friend FiniteField operator/(const G& y, const FiniteField& rhs) {
    FiniteField res;
    res.x = res.normalize(y);
    return res / rhs;
  }
  template <class G>
  FiniteField operator^=(G k) {
    if (k == 0) {
      x = 1;
      return *this;
    }
    T t = x;
    k--;
    while (k > 0) {
      if (k & 1) x = mul()(x, t, p);
      t = mul()(t, t, p);
      k >>= 1;
    }
    return *this;
  }
  template <class G>
  FiniteField operator^(G k) const {
    if (k == 0) return 1;
    T r = x, t = x;
    k--;
    while (k > 0) {
      if (k & 1) r = mul()(r, t, p);
      t = mul()(t, t, p);
      k >>= 1;
    }
    return r;
  }
  friend istream& operator>>(istream& is, FiniteField& rhs) {
    is >> rhs.x;
    return is;
  }
  friend ostream& operator<<(ostream& os, const FiniteField& rhs) {
    os << rhs.x;
    return os;
  }
};
template <class T>
class mul {
 public:
  T operator()(const T& x, const T& y, const T& p) {
    return (long long)x * y % p;
  }
};
template <class T>
class dvd {
 public:
  T operator()(const T& x, const T& y, const T& p) {
    pair<T, T> r = euclid(y, p);
    return mul<T>()(x, (r.first % p + p) % p, p);
  }

 private:
  pair<T, T> euclid(T a, T b) {
    if (b == 0) return make_pair(1, 0);
    pair<T, T> r = euclid(b, a % b);
    return make_pair(r.second, r.first - a / b * r.second);
  }
};
const int maxn = 100000 + 5;
int m, n;
FiniteField<int, mul<int>, dvd<int> > a[maxn];
map<FiniteField<int, mul<int>, dvd<int> >, int> hs;
void solve() {
  cin >> m >> n;
  p = m;
  for (int i = (0); i < (n); i++) cin >> a[i];
  if (n == 1) {
    cout << a[0] << " " << 0 << "\n";
    return;
  }
  if (n == p) {
    cout << 0 << " " << 1 << "\n";
    return;
  }
  FiniteField<int, mul<int>, dvd<int> > sum = 0, sqsum = 0;
  for (int i = (0); i < (n); i++) sum += a[i], sqsum += a[i] * a[i], hs[a[i]];
  for (int i = (0); i < (n); i++) {
    FiniteField<int, mul<int>, dvd<int> > x = a[i];
    FiniteField<int, mul<int>, dvd<int> > d = (sum / n - x) * 2 / (n - 1);
    if (d == 0) continue;
    if (sqsum !=
        x * x * n + x * d * n * (n - 1) + d * d * (n - 1) * n * (2 * n - 1) / 6)
      continue;
    int ok = 1;
    for (int j = (0); j < (n); j++) {
      if (!hs.count(x + j * d)) {
        ok = 0;
        break;
      }
    }
    if (ok) {
      cout << x << " " << d << "\n";
      return;
    }
  }
  cout << -1 << "\n";
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  solve();
  return 0;
}
