cf988D

集合的大小不会超过三

#include<bits/stdc++.h>
#define forn(i, n) for (int i = 0 ; i < int(n) ; i++)
#define fore(i, s, t) for (int i = s ; i < (int)t ; i++)
#define fi first
#define se second
#define all(x) x.begin(),x.end()
#define pf2(x,y) printf("%d %d
",x,y)
#define pf(x) printf("%d
",x)
#define each(x) for(auto it:x)  cout<<it<<endl;
#define pii pair<int,int>
#define sc(x) scanf("%d",&x)
using namespace std;
typedef long long ll;
const int maxn=2e5+5;
const int maxm=2e5+5;
const int inf=1e9;
int main(){
	int n;
	cin>>n;
	vector<int> a(n); 
	for(int i=0;i<n;i++)
		cin>>a[i];
	sort(all(a));
	vector<int> ans = {a[0]};
	for(int i=0;i<n;i++){
		for(int j=0;j<31;j++){
			int lx=a[i]-(1<<j);
			int rx=a[i]+(1<<j);
			bool isl=binary_search(all(a),lx);
			bool isr=binary_search(all(a),rx);
			if(isl && isr && ans.size()<3) {
				ans={lx,a[i],rx};
			}
			if(isl && ans.size()<2) 
				ans={lx,a[i]};
			if(isr && ans.size()<2)
				ans={a[i],rx};
		}
	}
	cout<<ans.size()<<endl;
	for(auto it:ans)
		cout<<it<<' ';
	cout<<endl;
}