#include <bits/stdc++.h>
int nextInt() {
  int x;
  scanf("%d", &x);
  return x;
}
double nextDouble() {
  double x;
  scanf("%lf", &x);
  return x;
}
long long nextLong() {
  long long x;
  scanf("%I64d", &x);
  return x;
}
char nextChar() {
  char x;
  scanf("%c", &x);
  return x;
}
void newLine() { printf("\n"); }
long long powM(long long a, long long b, long long MOD) {
  long long x = 1, y = a;
  while (b > 0) {
    if (b % 2 == 1) {
      x = (x * y);
      if (x > MOD) x %= MOD;
    }
    y = (y * y);
    if (y > MOD) y %= MOD;
    b /= 2;
  }
  return x;
}
long long gcd(long long a, long long b) { return b == 0 ? a : gcd(b, a % b); }
long long lcm(long long a, long long b) { return (a * b) / gcd(a, b); }
int countSetBits(long long n) {
  int ans = 0;
  while (n != 0) {
    n -= (n & -n);
    ++ans;
  }
  return ans;
}
long long mod = 1000000007;
long long mod2 = 1000000009;
const int N = 200100;
const int M = 111;
const int LOG = 21;
const long long INF = 4e9;
const long double EPS = 1e-6;
const long double PI = 2 * acos(0);
using namespace std;
long long a[N];
map<long long, int> mp;
long long dp[N][35];
long long sol[N][35];
set<long long> st;
int main() {
  int n = nextInt();
  for (int i = 0; i < n; i++) {
    a[i] = nextLong();
    st.insert(a[i]);
  }
  sort(a, a + n);
  for (int i = 0; i < n; i++) mp[a[i]] = i + 1;
  for (int i = 0; i < N; i++) {
    for (int j = 0; j < 35; j++) {
      dp[i][j] = INF;
    }
  }
  for (int i = 0; i < n; i++) {
    long long t = 1;
    for (int j = 0; j < 35; j++) {
      if (dp[i][j] == INF) {
        dp[i][j] = 1;
        sol[i][j] = i;
      }
    }
    for (int j = 0; j < 35 && t < INF; j++) {
      if (st.find(a[i] + t) != st.end()) {
        int c = mp[a[i] + t] - 1;
        if (dp[c][j] > dp[i][j] + 1) {
          dp[c][j] = dp[i][j] + 1;
          sol[c][j] = i;
        }
      }
      t *= 2;
    }
  }
  int I, J;
  int ans = 0;
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < 35; j++) {
      if (dp[i][j] > ans) {
        ans = dp[i][j];
        I = i;
        J = j;
      }
    }
  }
  set<long long> v;
  while (true) {
    v.insert(a[I]);
    if (sol[I][J] == I) break;
    I = sol[I][J];
  }
  cout << min((int)v.size(), 3) << endl;
  int k = 0;
  for (auto p : v) {
    cout << p << " ";
    k++;
    if (k == 3) break;
  }
}
