#include <iostream>
#include <iomanip>

using namespace std;

constexpr const char * convert(char hx)
{
    constexpr const char * hex[16] = {
        "0000","0001","0010","0011",
        "0100","0101","0110","0111",
        "1000","1001","1010","1011",
        "1100","1101","1110","1111" };
    if (hx >= '0' && hx <= '9') return hex[hx-'0'];
    else if (hx >= 'A' && hx <= 'F') return hex[hx-'A'+10];
    else if (hx >= 'a' && hx <= 'f') return hex[hx-'a'+10];
    return nullptr;
}



int main(int argc, const char * argv[])
{
    constexpr auto x = convert('F'); // x = "1111"
    cout << x << endl;
    char y = '1';
    const auto z = convert(y);
    cout << z << endl;
}