#include<bits/stdc++.h>
#define LL long long
#define ULL unsigned long long#define scs(i) scanf("%s", i)
#define sci(i) scanf("%d", &i)
#define scd(i) scanf("%lf", &i)
#define scl(i) scanf("%lld", &i)
#define scIl(i) scanf("%I64d", &i)
#define scii(i, j) scanf("%d %d", &i, &j)
#define scdd(i, j) scanf("%lf %lf", &i, &j)
#define scll(i, j) scanf("%lld %lld", &i, &j)
#define scIll(i, j) scanf("%I64d %I64d", &i, &j)
#define sciii(i, j, k) scanf("%d %d %d", &i, &j, &k)
#define scddd(i, j, k) scanf("%lf %lf %lf", &i, &j, &k)
#define sclll(i, j, k) scanf("%lld %lld %lld", &i, &j, &k)
#define scIlll(i, j, k) scanf("%I64d %I64d %I64d", &i, &j, &k)#define lson l, m, rt<<1
#define rson m+1, r, rt<<1|1
#define lowbit(i) (i & (-i))
#define mem(i, j) memset(i, j, sizeof(i))#define fir first
#define sec second
#define ins(i) insert(i)
#define pb(i) push_back(i)
#define pii pair<int, int>
#define mk(i, j) make_pair(i, j)
#define all(i) i.begin(), i.end()
#define pll pair<long long, long long>#define _TIME 0
#define _INPUT 0
#define _OUTPUT 0
clock_t START, END;
void __stTIME();
void __enTIME();
void __IOPUT();
using namespace std;
const int maxn = 2e5 + 10;
LL arr[maxn];int main(void){__stTIME();__IOPUT();set<LL> s;int n;sci(n);for(int i=1; i<=n; i++){scIl(arr[i]);s.ins(arr[i]);}LL ans1, ans2, ans3;bool _3 = false;bool _2 = false;for(int i=0; i<=30; i++){for(int j=1; j<=n; j++){if(s.count(arr[j]+(1LL<<i))){if(!_2){_2 = true;ans1 = arr[j];ans2 = arr[j]+(1LL<<i);}if(s.count(arr[j]-(1LL<<i))){if(!_3){_3 = true;ans1 = arr[j]-(1LL<<i);ans2 = arr[j];ans3 = arr[j]+(1LL<<i);}}}if(_3) break;}if(_3) break;}if(_3){puts("3");return !printf("%I64d %I64d %I64d\n", ans1, ans2, ans3);}if(_2){puts("2");return !printf("%I64d %I64d\n", ans1, ans2);}printf("1\n%I64d\n", arr[1]);__enTIME();return 0;}void __stTIME()
{#if _TIMESTART = clock();#endif
}void __enTIME()
{#if _TIMEEND = clock();cerr<<"execute time = "<<(double)(END-START)/CLOCKS_PER_SEC<<endl;#endif
}void __IOPUT()
{#if _INPUTfreopen("in.txt", "r", stdin);#endif#if _OUTPUTfreopen("out.txt", "w", stdout);#endif
}