Counting ones

input/code.cpp: In function 'int main(int, char**)':
input/code.cpp:19:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long unsigned int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   19 |     for (int i=0; i<numbers.size(); i++) {
      |                   ~^~~~~~~~~~~~~~~
input/code.cpp:20:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long unsigned int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   20 |         for (int j=i+1; j<numbers.size(); j++) {
      |                         ~^~~~~~~~~~~~~~~
In file included from /usr/include/c++/13/iostream:41,
                 from input/code.cpp:1:
In member function 'std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long long unsigned int) [with _CharT = char; _Traits = std::char_traits<char>]',
    inlined from 'int main(int, char**)' at input/code.cpp:33:18:...

#include <iostream>
#include <vector>
#include <bitset>


int main(int argc, char **argv) {
    int n;
    std::cin >> n;

    std::vector<unsigned long long> numbers(n);
    for (int i=0; i<n; i++) {
        std::cin >> numbers[i];
    }

    int best_numbers_of_ones = 0;
    unsigned long long a;
    unsigned long long b;

    for (int i=0; i<numbers.size(); i++) {
        for (int j=i+1; j<numbers.size(); j++) {
            std::bitset<64> multiplication_in_bits = numbers.at(i) * numbers.at(j);
            int numbers_of_ones = multiplication_in_bits.count();

            if (numbers_of_ones > best_numbers_of_ones) {
                best_numbers_of_ones = numbers_of_ones;
                a = numbers.at(i);
                b = numbers.at(j);
            }
        }
    }

    std::cout << best_numbers_of_ones << std::endl;
    std::cout << a << " " << b << std::endl;

    return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED