#include <iostream>
#include <bitset>
#include <climits>
void print_bin(int num)
{
    std::string bin = std::bitset<CHAR_BIT * sizeof num>(num).to_string();
    // trim leading zeroes
    bin = num ? bin.substr(bin.find('1')) : "0";
    std::cout << num << ": [0B" << bin << ']' << '\n';
}
int main()
{
    print_bin(5);
    print_bin(42);
}