#include <bits/stdc++.h>
using namespace std;
template <typename T, typename T1>
ostream &operator<<(ostream &out, pair<T, T1> obj) {
  out << "(" << obj.first << ", " << obj.second << ")";
  return out;
}
template <typename T, typename T1>
ostream &operator<<(ostream &out, map<T, T1> cont) {
  typename map<T, T1>::const_iterator itr = cont.begin();
  typename map<T, T1>::const_iterator ends = cont.end();
  for (; itr != ends; ++itr) out << *itr << " ";
  out << endl;
  return out;
}
template <typename T>
ostream &operator<<(ostream &out, set<T> cont) {
  typename set<T>::const_iterator itr = cont.begin();
  typename set<T>::const_iterator ends = cont.end();
  for (; itr != ends; ++itr) out << *itr << " ";
  out << endl;
  return out;
}
template <typename T>
ostream &operator<<(ostream &out, multiset<T> cont) {
  typename multiset<T>::const_iterator itr = cont.begin();
  typename multiset<T>::const_iterator ends = cont.end();
  for (; itr != ends; ++itr) out << *itr << " ";
  out << endl;
  return out;
}
template <typename T,
          template <typename ELEM, typename ALLOC = allocator<ELEM>> class CONT>
ostream &operator<<(ostream &out, CONT<T> cont) {
  typename CONT<T>::const_iterator itr = cont.begin();
  typename CONT<T>::const_iterator ends = cont.end();
  for (; itr != ends; ++itr) out << *itr << " ";
  out << endl;
  return out;
}
template <typename T, unsigned int N, typename CTy, typename CTr>
typename enable_if<!is_same<T, char>::value, basic_ostream<CTy, CTr> &>::type
operator<<(basic_ostream<CTy, CTr> &out, const T (&arr)[N]) {
  for (auto i = 0; i < N; ++i) out << arr[i] << " ";
  out << endl;
  return out;
}
template <typename T>
T gcd(T a, T b) {
  T min_v = min(a, b);
  T max_v = max(a, b);
  while (min_v) {
    T temp = max_v % min_v;
    max_v = min_v;
    min_v = temp;
  }
  return max_v;
}
template <typename T>
T lcm(T a, T b) {
  return (a * b) / gcd(a, b);
}
template <typename T>
T fast_exp_pow(T base, T exp, T mod) {
  T res = 1;
  while (exp) {
    if (exp & 1) {
      res *= base;
      res %= mod;
    }
    exp >>= 1;
    base *= base;
    base %= mod;
  }
  return res % mod;
}
int N;
long long maxVal = -9999999999;
long long coords[200010];
map<long long, bool> exists;
int main() {
  scanf("%d", &N);
  for (auto i = 0; i < N; ++i) {
    scanf("%lld", coords + i);
    exists[coords[i]] = true;
    maxVal = max(maxVal, coords[i]);
  }
  sort(coords, coords + N);
  for (long long Tpow = 1; Tpow < 9999999999; Tpow *= 2LL) {
    for (auto i = 0; i < N; ++i) {
      if ((coords[i] + 2 * Tpow) > maxVal) {
        break;
      }
      if (exists[coords[i] + Tpow] && exists[coords[i] + 2 * Tpow]) {
        printf("3\n%lld %lld %lld\n", coords[i], coords[i] + Tpow,
               coords[i] + 2 * Tpow);
        return 0;
      }
    }
  }
  for (long long Tpow = 1; Tpow < 9999999999; Tpow *= 2) {
    for (auto i = 0; i < N; ++i) {
      if (coords[i] + Tpow > maxVal) {
        break;
      }
      if (exists[coords[i] + Tpow]) {
        printf("2\n%lld %lld\n", coords[i], coords[i] + Tpow);
        return 0;
      }
    }
  }
  printf("1\n%lld\n", coords[0]);
  return 0;
}
