func_code_string: #include <bits/stdc++.h>   using namespace std;   template <typename T, typename U>   std::pair<T, U> operator+(const std::pair<T, U>& l, const std::pair<T, U>& r) {     return {l.first + r.first, l.second + r.second};   }   typedef void (*callback_function)(void);   const long long ZERO = 0LL;   const long long INF64 = 1e18;   const long long INF32 = 1e9;   const long long MOD = 1e9 + 7;   const long double PI = acos(-1.0L);   const long double EPS = static_cast<long double>(1e-9);   const long long N = 1e6 + 7;   long long n, a[N], del;   void input() {     cin >> n;     for (long long i = (1); i <= (n); i++) {       cin >> a[i];     }   }   void solve() {     map<long long, long long> mp;     for (long long i = (1); i <= (n); i++) {       while (mp[a[i]]) {         a[mp[a[i]]] = 0;         mp[a[i]] = 0;         a[i] *= 2;         del++;       }       mp[a[i]] = i;     }   }   void output() {     cout << n - del << endl;     for (long long i = (1); i <= (n); i++) {       if (a[i]) cout << a[i] <<    ;     }     cout << endl;   }   int main() {     ios_base::sync_with_stdio(false);     cin.tie();     {       input();       solve();       output();     }     return 0;   }   