#include <bits/stdc++.h>
using namespace std;
int main() {
  std::ios::sync_with_stdio(false);
  std::cin.tie(0);
  long long n;
  cin >> n;
  vector<int> v(n);
  for (int i = (0); i < (n); ++i) cin >> v[i];
  sort(v.begin(), v.end());
  vector<int> res = {v[0]};
  for (int i = (0); i < (n); ++i)
    for (int j = (0); j < (31); ++j) {
      int lx = v[i] - (1 << j);
      int rx = v[i] + (1 << j);
      bool isl = binary_search(v.begin(), v.end(), lx);
      bool isr = binary_search(v.begin(), v.end(), rx);
      if (isl && isr && int(res.size()) < 3) {
        res = {lx, v[i], rx};
      }
      if (isl && int((int)res.size()) < 2) {
        res = {lx, v[i]};
      }
    }
  cout << (int)res.size() << endl;
  for (auto it : res) cout << it << " ";
}
