my template , C++ (gcc)

my template

/*  
     author : masaow    
     g++ : 17.3.20  
*/        
#include <bits/stdc++.h>  
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
#define forn(i,a,b)        for( i = a ; i < b  ; i++ )
#define debug(x)           cout << #x << " " << x << " -- "
#define I__O               ios::sync_with_stdio(false),cin.tie(NULL),cout.tie(NULL)
#define ll                 long long  
#define p(x)               cout << x << "\n" ; 
#define MOD                100000007
#define pi                 pair<int,int>
#define vi                 vector <int>
#define pb                 push_back
#define vp                 vector <pair<ll,ll>>
#define endl               cout << "\n"
#define mi                 map <int,int> 
#define f1                 first 
#define s1                 second    
#define in                 insert
#define all(x)             x.begin(),x.end() 
using namespace std ; 
using namespace __gnu_pbds;
typedef tree<int,null_type,less<int>,rb_tree_tag,
tree_order_statistics_node_update> indexed_set ; 
const int N = 2e5+7;  
/*  
    time : 10 : 14    
    date : 22.01.2020
*/    
// int L,R,mid,target,idx ;
int a[N] ; 
int tests() 
{   
    int i,j;  
    int n ; cin >> n;  
    set <int> s; 
    forn(i,0,n){
        cin >> a[i] ; 
        s.insert(a[i]) ; 
    } 
    forn(i,0,n){
        set <int> vec ; 
        vec.insert(a[i]) ; 
        forn(j,0,31) 
            if(s.find(a[i]+(1<<j)) != s.end() && (s.find(a[i]-(1<<j)) != s.end())){
            vec.insert(a[i]+(1<<j)), vec.insert(a[i]-(1<<j)) ;
            cout << vec.size() << '\n' ; 
            for(auto &x : vec)
                cout << x << ' ' ; 
            return 0 ; 
            } 
    }
     forn(i,0,n){
        set <int> vec ; 
        vec.insert(a[i]) ; 
        forn(j,0,31) 
            if( s.find(a[i]+(1<<j)) != s.end() ){
            vec.insert(a[i]+(1<<j));
            cout << vec.size() << '\n' ; 
            for(auto &x : vec)
                cout << x << ' ' ; 
            return 0 ; 
            } 
            else if( s.find(a[i]-(1<<j)) != s.end() ){
            vec.insert(a[i]-(1<<j)) ; 
            cout << vec.size() << '\n' ; 
            for(auto &x : vec)
                cout << x << ' ' ; 
            return 0 ; 
            }
     }
    
        cout << 1 << '\n' << a[0] << '\n' ; 
        return 0 ; 
}
int main(){
    I__O ;  
    int cases = 1 ; 
    //cin >> cases;  
    while(cases--)
      tests(); 
  return 0 ; 
}


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